The CompsAPI blog

eBay Sold Prices in Google Sheets
17 October 2026
Put real completed eBay sale prices in a spreadsheet with a formula. The four functions, how to set them up in about a minute, and the three things eBay's public sold page will not give you.

Why Your Card Comps Are Wrong
17 October 2026
The same search, the same three years of eBay sales, two medians: $14.73 and $545.00. Measured 17 October 2026. What keyword matching does to a card comp, and the four filters that fix it.

Pricing an Item With No Recent Sales
17 October 2026
eBay's sold page shows about 90 days. For anything rare that window is often empty, and an empty window is not a price of zero. Four ways to price a thin market, and when to widen the window instead.

We Changed One Parameter and the Median Moved 10x
17 October 2026
60 products, two time windows, one query each. On 16% the median moved more than 10% and on one it moved 10x, with no change in the market. A measurement of what time windows do to an unfiltered comp.

Price a CSV of Items From Real eBay Sales
17 October 2026
A working script that reads a CSV of items and writes back a median, a 25th to 75th band and the sample size each number rests on. Rate limits, caching, retries and the rows you should not trust.

Valuing an Estate Lot Before You Bid
17 October 2026
A real ten item lot priced from completed eBay sales. One row was wrong by 7x and moved the whole lot valuation by a fifth. How to find that row, and the price floor trick that fixed it.

What goes here

Measurements, and how to get a number you can act on out of completed eBay sales. Every figure on this blog comes from a dated run against our own API and says how many sales it rests on. Where our own data looks bad, it says that too.

The reference material lives elsewhere: the API reference, the Best Offer gap study, and a comparison of every eBay sold data API.