The maximum bid for your margin: working backwards

"Up to what bid do I still make money?" is the main question at an auction. You can calculate the answer in advance if you start from the sale price, not from the bid.

The idea

If the target margin is t and the expected sale price is M, the cost cannot exceed M × (1 − t). The cost depends on the bid L (auction fees, duty and VAT all grow with it), so we look for the largest L for which

cost(L) ≤ M × (1 − t).

An example from the demo on the home page: sale price $16,500, target 15%. The maximum cost is $14,025. For Ukraine with typical tariffs that corresponds to a bid of no more than $2,475. The current bid of $3,000 gives 10.3% margin, which is below target.

Why one equation is not enough

Auction fees change in steps: the buyer fee depends on the price bracket, and the online bid fee has its own brackets. At a bracket boundary the cost can jump by tens of dollars because of a single extra dollar of bid. So a simple "multiply and divide" formula will not do.

How ImportOS searches

1. It splits the bid range into segments at the boundaries of the fee tables.
2. It goes from the top segment downwards and checks the lower point of each (that is where margin is best).
3. In the first segment that fits, it finds the largest bid by binary search with the step you set (auctions accept whole-dollar bids, with increments from $25).

This guarantees that the bid found is truly the maximum, even when the fee table is not monotonic.

How to use it

• For every lot, write down not only "I bid up to X" but also your assumption about the sale price: X depends on it.
• Recalculate X when the exchange rate or your tariffs change.
• Leave a cushion for repair: use the upper end of the range.

In the ImportOS Margin extension, "maximum bid for margin X" is shown next to the lot, and in the demo on the home page you can see how it changes with the country and the sale price.