Doorbuster maths done right: break-even attach rate, profit per 100 promo sales, sensitivity table & doorbuster-vs-sitewide verdict.
Selling something at a loss on purpose sounds mad â until the maths works. A doorbuster is an investment: you lose a little on the hero item to pull in baskets full of full-margin companions. This planner tells you exactly what attach rate you need to break even, what you earn per 100 promo sales, and whether a plain sitewide discount would quietly make you more.
Enter the doorbuster's true unit cost and promo price, how many units you'll allow (set a hard cap â this is your guardrail), then your expected attach rate: the share of doorbuster buyers who add full-price items, and the average margin those baskets carry. The comparison section pits your doorbuster against a flat sitewide discount on your normal AOV and margin.
Break-even attach rate. If it's under ~30%, most decent promos clear it. If it's 50%+, you're betting the promo on behaviour most stores never see â redesign the offer (raise the doorbuster price a little, add a minimum-basket gift, or pick a cheaper hero item) before you launch. And never let companion items stock out mid-promo: a doorbuster with nothing to attach to is just a loss.
Check per-SKU discount depth in the Sale Discount Planner, and make sure your ad budget survives November in the Holiday Ad Cost Surge Planner.
Most stores see 15â35% of doorbuster buyers adding full-price items. Above 50% is rare and usually means the 'companion' items were really the draw. Model the â20 point sensitivity row as your downside case.
Yes â always. An uncapped loss-leader that goes viral is the classic way to lose thousands in a weekend. Set the cap at the number your break-even maths was built on, and kill the promo the moment it hits.
When your attach rate or companion margin is weak. Sitewide discounts are boring but predictable â the comparison table shows you per 100 transactions so the trade-off is explicit.
Then the doorbuster becomes pure loss with no recovery path. Hold back safety stock on your top 20% companion SKUs before launch, and pause the hero item rather than run it naked.
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