How GavelGap tested SoldStack on 3,772 auction lots
GavelGap, a GovDeals pricing tool, compared SoldStack's values with what bidders actually paid. SoldStack came in below the winning bid on 9% of lots, versus 34% for GavelGap's own estimates.
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The test
GavelGap scores GovDeals surplus listings for resale profit. Clothing lots were its weakest category, so it sent SoldStack 3,772 clothing, shoe and bag lots that closed between May and October 2026, each with its winning bid.
SoldStack read each listing into items (brand, item, condition, quantity) and valued them from cleaned Poshmark sales. GavelGap then scored those values against its own estimates.
A winning bid is what a reseller paid, so a good resale value should normally land above it. A value below the winning bid, especially when several people bid, is a warning sign that the estimate is too low.
The result
| Lots scored by both tools | SoldStack below the winning bid | GavelGap's own estimates below it |
|---|---|---|
| All | 9% | 34% |
| 3 or more bidders | 20% | 51% |
Lots that list their items one by one did best: across 639 of them, SoldStack's value was a median 2.0 times the winning bid, and 85% came in above it.
Where it doesn't fit
- Single items came out around 1 times the winning bid for both tools: bidders push one branded item close to its resale value.
- Bulk commodity lots (2,100 plain briefs, 200 belts) can come out 10 times the winning bid or more. Online single-item prices don't carry over to bulk basics without a steep discount.
- Pallets sold by weight need a unit count before any per-item value means anything.
How GavelGap uses SoldStack
One call to POST /v1/value per lot, with each item's brand, description, condition and quantity. Each item counts as one lookup. Items with a brand and model are valued from exact-model sales, and the rest fall back to their category and condition. Details are in the API docs.