Auctimate

Five real lots from GSA Auctions, the US government's surplus marketplace, and you have to say what each one actually sold for. The catalogue it draws from is gloriously strange: a 27-foot patrol boat, a men's Breitling, a laboratory cryostat listed in repairable condition, mobile X-ray systems. You get the photographs and the auctioneer's own dry description, then a single number to type, and the real hammer price appears the moment you commit.

1. Read the lot. The title, the model numbers, the condition line and the year of sale all come straight from the listing, and the condition line is doing more work than it looks.
2. Page through the photographs with the arrows. A lot carries three to five of them, and they are the auction's own shots, not marketing images.
3. Type your figure in dollars and hit Submit guess. One guess, no ranges, no direction hint.

Most price-guessing games use retail listings, where you are really being tested on how much attention you pay to shopping. Auctimate uses government surplus, where the price is whatever a room of bidders decided on a specific day, and that number obeys rules almost nobody has an intuition for. You start out wildly wrong, and the interesting part is that you get better fast, because the lots keep teaching you the same lesson about condition and liquidity. It is free, one guess per lot keeps it honest, and the round-by-round breakdown at the end shows how everyone else read the same photographs.

Brutally simple: no higher or lower, no second try. Your figure and the real price sit side by side, and the gap is converted into points up to 1,000 for that lot. The wording tells you which band you fell in, from Far off through Solid estimate and Close estimate to Excellent estimate. Being an order of magnitude out scores a flat zero: $250,000 on a piece of lab equipment that went for a fraction of it earns nothing. The scale is unforgiving in a way that suits the subject, because auction prices do not negotiate either.

Daily challenge

Five lots a day, scored out of 5,000, with a leaderboard for the day and a countdown to the next set. A Replay button lets you run the current day's lots again.

• Read the condition line before you look at the photos. Repairable, used, operational when taken out of service, these phrases move the price far more than the item's retail value does, and surplus buyers price them accordingly.
• Anchor low. Government surplus clears at liquidation prices, not catalogue prices, so a machine worth six figures new can go for a few thousand and your instinct from retail listings will be consistently too high.
• Specialist gear is where the real money is. Lots that look like ordinary industrial junk, marine hulls with working engines, complete medical imaging systems, hold their value far better than the consumer items in the mix.