BFCM in eCommerce: how to stay profitable when everyone is slashing margins

Every year it's the same story. Late November, everyone stares at the revenue on their dashboard and pats themselves on the back. Nice growth, big volume, records smashed. Then January rolls in. Returns pile up, refunds leave the account, the post-sale slowdown kicks in, and that's when the real profit number shows up. Usually a lot uglier than the November snapshot.

BFCM isn't a revenue contest. It's a contribution margin contest. And most brands forget that when they're building their offers.

I'm going to walk you through how we approach this period with our clients, and above all the single filter that matters before you launch anything. A real Black Friday eCommerce strategy is exactly that, not a list of promos thrown out at random.

The only number that matters, and it won't show up the next day

Contribution margin is what's left once you've stripped out product cost, shipping, payment fees, expected returns and media spend. Not gross revenue. Not the ROAS showing in your Business Manager. What actually lands in your pocket.

And you can't read that number the morning after Cyber Monday. Your November scoreboard is provisional. The real one lands in January, once returns have been processed and support tickets are closed. So you plan on the stabilised number, not the peak.

This answers a question everyone asks before BFCM. What discount rate can I offer without blowing everything up? The answer isn't a magic figure. It depends on your product margin after all costs. If at 20% off you're still profitable on an item and at 25% you're not, your ceiling is 20%. It's that simple, but until you've nailed down your true margin per product, you're discounting blind.

The test to run before every tactic fits on one line. Does this increase my contribution margin after COGS, shipping, payment fees, estimated returns and media? If the answer is no, you don't launch it. It's that simple.

Stop slashing your best-sellers

The first mistake is putting your already-selling products on promo. You're handing margin to customers who were going to buy anyway. It's called pull-forward, you move a future full-price sale into a discount window and call it growth. That's not growth, it's margin you're throwing away.

Before you decide HOW to discount, decide WHAT to discount. What we tell our clients is to save the big discounts for overstock and old collections. I'd much rather a customer walks away with a discounted product from a past collection than have it rot in a warehouse. That's cash doing work. Your heroes, you protect.

And while we're on best-sellers, one reflex too many brands skip. Sync your stock before the sale. You open the floodgates in late November, your flagship product goes out of stock or you oversell, and you spend the whole weekend managing cancellations and angry customers. The tactics below are worthless if your logistics can't keep up.

Incentives that don't eat your margin

There are plenty of ways to create value for the customer without handing them a big chunk of your profit. That's the heart of a good Black Friday promo idea, make it feel like a great deal without slashing prices.

Bundles work well. You combine several products into a pack priced slightly below buying them separately. The customer feels they're getting more for their money even if the per-item discount is modest. You pick the right products to pair up, and you protect your overall margin.

Tiered discounts, too. You offer 10% off at 50 euros, 15% at 100, 20% at 150. The customer adds items to hit the next tier, and your average order value climbs. The discount becomes an AOV driver instead of a hole in your margin.

And the free gift instead of a discount. A sample, a branded accessory, a limited-edition piece. The perceived value of the gift often exceeds its real cost to you. It's also a great way to clear slow-moving stock, as long as you position it as exclusive and not as a bottom-of-the-drawer leftover. There you go, you lift AOV without torching your margin.

Talk differently to your best customers

Blasting the same offer to your entire base is the lazy reflex. Not all your customers are deal-hunters.

Segmentation is extremely profitable and cheap to set up. In Klaviyo, we systematically build VIP segments around BFCM. Three ways to define them.

• Big spenders, those who've spent above a certain amount over the last 365 days
• Frequent buyers, a specific number of orders over the year
• The mixed approach that combines spend and frequency to catch your genuinely valuable customers

Once these VIPs are identified, you don't throw them a coupon like everyone else. You give them early access, exclusive launches, personalised bundles. You deepen loyalty and keep your margin intact. A loyal customer who gets an exclusive invite instead of a dumb discount is a customer who buys at full price and feels privileged.

Lift the average order value while they're already there

When people are on your site in the thick of BFCM, they're hot. It's the best moment to cross-sell and up-sell. It's also the real answer to the question "how do I increase order value without lowering my prices", you work the cart, not the discount.

On-site product recommendations work well. If you're a footwear brand and a customer is looking at running shoes, you show a "complete your running kit" block with socks, shorts, a water bottle. On already-high carts, a Klaviyo pop-up with a cheap impulse-buy product pushes AOV up a few euros on every order. Tools like OrderEditing also let the customer modify their order before shipping without going through support, which opens one more window to add an item.

And cross-selling doesn't stop at checkout. We set up post-purchase flows for our clients. A personalised recommendation a few weeks after BFCM, or a one-time offer on a related product right after the order. That's revenue you're pulling from people who already trust you, so at an acquisition cost close to zero.

Optimise your ads on profit, not on reported ROAS

On the acquisition side, the trap is steering by raw ROAS. ROAS counts the best-seller sales you'd have made without ads, it counts carts before returns, it doesn't count your product margin.

What we look at is profit on ad spend. We push high-margin products into the campaigns, not the ones that return zero once the discount is applied. And we build audiences on CLV and high-intent behaviours, not just broad lookalikes.

There's another question that comes up constantly. How do you keep acquisition costs from exploding and eating your margins during BFCM? The answer is anticipation. In the run-up to BFCM, take advantage of lower costs to run top-of-funnel. Video views, consideration, traffic. You'll degrade your profitability a bit in October and early November, yes. But you build audience pools wide enough to retarget in late November, and that's when your acquisition costs drop massively right as the volume shows up. You just have to look at the delta across the whole period, not month by month. Otherwise you panic in October and cut exactly what's going to win you November.

And a new customer acquired at low margin, even at a loss, isn't necessarily a disaster. As long as you know they'll buy again. That's the whole point of the next section.

Keep them after BFCM

The customer you acquire during BFCM, if they buy once and vanish, you paid a lot for nothing. Lasting profitability is decided on the second order. That's why a slightly high CPA on day one can be profitable, if your second and third orders follow.

Post-purchase flows are for exactly that. Cut returns first, because every return eats the margin you thought you'd made. A satisfaction survey to understand what went wrong. Personalised follow-up campaigns to turn the November buyer into a repeat customer.

One thing to know about CRM during BFCM. Since everyone's sending aggressive campaigns, open rates mechanically drop. So a newsletter featuring your best-sellers really needs to be seen by your base. What works well is offering express shipping a few days before the Christmas delivery cut-off. It creates real urgency, not manufactured, and it pushes the last fence-sitters to order. For our clients, Klaviyo often drives at least 30% of revenue over these periods. It's not an option, it's where a big chunk of the margin is made because the cost is near zero.

What you do Monday morning

Before finalising your BFCM offers, pull out your eCommerce P&L. Lay down your true margin per product, estimated returns included. You'll get some surprises, some good, some bad, but at least you won't have any surprise once the sale is over.

Then you apply the filter to every tactic. Does this increase my contribution margin after all costs? You keep your best-sellers at full price, you dump your slow stock as a gift or in a bundle, you talk differently to your VIPs, and you steer your ads on profit not ROAS.

And above all, once the dust settles, you analyse. Which offers actually made margin, which products cost you cash, which segment responded best. That debrief is what builds next year's strategy. Because the real number is the one that's left once the dust has settled, not the November snapshot.