Guide
Price is the single biggest lever in eBay's Best Match algorithm for Buy It Now listings. Undercutting the lowest competitor reliably wins more impressions and the coveted buy box position — but unclamped repricing is a trap. Sellers who race to the bottom without a hard floor can wind up selling below cost within hours of a competitor's next move. The only sustainable path is automated repricing that beats the market price and refuses to go below a floor you control, per item, before a single sale happens.
eBay's Best Match ranking for Buy It Now listings weighs several factors: seller feedback score, shipping speed, return policy, and — critically — price competitiveness. eBay does not publish exact weights, but its own seller guidance confirms that listings priced closer to the lowest available are more likely to surface at the top of search results and win the buy box when multiple sellers offer the same or similar item. In practice, even a $0.50 gap below a competitor can shift visibility. The implication is direct: if you are not actively tracking and responding to competitor price changes, you are ceding buy box time to whoever repriced last.
Most repricing tools simply find the lowest competitor price and match or beat it by a fixed amount. That works until a competitor misprices an item, drops to $0.01, or a bot sets off a price war. Without a floor, your repricer follows all the way down. A seller in the electronics category who sets a $0.01 undercut rule with no floor on a $45 USB hub can wake up to 200 units sold at $3.12 — the price two bots ratcheted down to overnight. The floor is not an optional feature. It is the mechanism that makes automated repricing safe to leave running.
Your floor is the lowest price at which selling the item still makes financial sense. The standard formula accounts for four inputs: landed cost, shipping cost, eBay fee percentage, and your minimum acceptable margin. Here is a worked example for a mid-range kitchen gadget sold in the Home & Garden category:
Cost of goods: $8.00 Outbound shipping: $4.00 eBay final value fee (13.25% of sale price including shipping): variable Minimum margin: 15%
To solve for floor price F where profit margin is at least 15%: F = (cost + shipping) / (1 − fee% − margin%) F = ($8.00 + $4.00) / (1 − 0.1325 − 0.15) F = $12.00 / 0.7175 F ≈ $16.73
Round up to $17.00 or $17.14 to add a small buffer. That number goes into Undercut as the hard floor for that listing. The repricer will beat any competitor above $17.14 — and refuse to move below it under any circumstance.
The buy box is reassigned continuously. A repricer that checks prices once per day is functionally useless for competitive categories. On Undercut's Pro and Scale plans, listings reprice every 15 minutes. For high-velocity categories like consumer electronics, media, or health products where dozens of sellers compete on the same GTIN, 15-minute repricing means you recapture the buy box price within one cycle of any competitor move. For lower-competition niches — vintage items, handmade, or single-SKU listings — even hourly repricing is often sufficient, making the Free or Starter plan adequate. Match your repricing cadence to the actual competition density in your category.
Undercut connects to your eBay account via the standard eBay API. During onboarding, you import your active listings. For each listing, you set a floor price in the dashboard. Once floors are set, you choose your undercut amount: beat the lowest competitor by a fixed amount (e.g. $0.10) or by a percentage (e.g. 1%). From that point forward, Undercut monitors competitor prices and adjusts your listing price downward to stay at the buy box position, stopping the moment the next move would breach your floor. On the Pro and Scale plans, AI aggressiveness tuning lets you set, per listing, how close to the floor you are willing to operate — useful for margin-sensitive SKUs where you would rather lose the buy box than compress profit further.
Start repricing up to 25 listings free — 14-day trial, no credit card. Your floor is locked in before your first sale.
Start freeDoes winning the buy box always require having the lowest price on eBay?
Not always the absolute lowest on eBay as a whole, but you generally need to be the lowest among eligible sellers for that specific listing format. A seller with excellent feedback and fast handling can sometimes hold the buy box at a slightly higher price than a low-feedback competitor, but the gap is small — typically under 3-5%. Price remains the primary variable you can move quickly.
What happens if I set a floor and a competitor prices below it?
Undercut holds your listing at your floor price and does not follow the competitor below it. You will lose the buy box for that period. That is the correct outcome — selling below your floor means selling at a loss or at an unacceptable margin. When the competitor raises their price or sells out, Undercut automatically recaptures the buy box.
How do I know if my floor is set correctly?
Run the floor formula: (cost + shipping) / (1 − eBay fee% − minimum margin%). For most categories, eBay's final value fee is 13.25% on the total including shipping. Add your minimum acceptable margin — 15% is a common baseline. If you are consistently losing the buy box to a competitor who is pricing below your floor, that competitor is likely selling at a loss or has lower costs than you; following them down is not a viable strategy.
Is automated repricing against eBay's rules?
No. eBay explicitly supports third-party repricing tools through its official API. Undercut uses the eBay API to update listing prices programmatically, which is a standard, permitted seller activity. eBay's policies restrict certain listing manipulation tactics, but price updates via the API are not among them.
How many listings do I need before automated repricing pays for itself?
It depends on your margins and competition density, but most sellers find that even 10-15 competitive listings benefit from automated repricing. If even one listing wins the buy box an additional 20% of the time due to faster repricing, and that listing moves $500/month in GMV, the incremental revenue typically exceeds the Starter plan cost. Use the 14-day free trial to measure buy box percentage before and after enabling repricing on your top listings.
Related: What Is the eBay Buy Box? · What Is a Price Floor? · How to Avoid Selling Below Cost on eBay · Repricing Without Losing Margin · eBay Pricing Strategy Guide · Setting an eBay Price Floor