The lowest price you can accept before a sale starts costing you money — and the price that also keeps the margin you want. This is the number a repricer needs before it can safely move anything.
Sets the commission below
What the unit cost you, excluding VAT you reclaim
What postage actually costs you
Include any advertising commission you pay
Set to 0 if you are not VAT registered
Added on top of break-even. This is the number to use as your floor.
Below this you lose money on every unit
Break-even plus the margin you asked for
How it works: cost is grossed up, not marked up. Every percentage charge comes off the selling price, so break-even = cost ÷ (1 − commission − VAT). At a 15% fee with 20% VAT, £10 of cost needs £15.38, not £13.50.
Background
The most common way to set a minimum price is to take the price you charge today and knock a bit off it. It is quick, and it is wrong, because it assumes the price you charge today is already correct. If it was set optimistically, the floor inherits the optimism. If it was set when your supplier was cheaper, the floor is now below break-even and nothing will tell you.
Commission and VAT are percentages of the selling price, not of your cost, so you cannot recover them by adding the same percentage to cost. At a 15% commission, adding 15% to £10 gives £11.50 — but 15% of £11.50 is £1.73, leaving £9.77 and a loss. Dividing instead of multiplying gives £11.76, where the commission of £1.76 leaves exactly the £10 you started with. Add VAT to the same calculation and the divisor grows again.
A repricer whose minimum price equals its current price has nowhere to go. It cannot undercut anyone, so it never wins the Buy Box, and it looks like it is working because it is running on schedule and reporting no errors. This is the single most common reason automated repricing appears to do nothing. A floor derived from cost does not have that failure mode.
Break-even is where you stop losing money, not where you should sit. The margin field above is deliberately separate so you can see both: the hard limit, and the softer number you actually want to defend. Set your minimum price to the second one and you keep room to compete without ever selling at a loss.
Re-Pricer derives this floor for every listing from your cost prices and refuses to price below it, whatever a competitor does.
Set a target margin once and Re-Pricer derives a floor for every listing from its cost, then never prices below it.