Caitlyn Jenner — used race suit for sale … and it ain’t cheap!

The Caitlyn Jenner collectible market is BOOMING … at least one auction house is hoping it is … selling one of CJ's used racing suits — and they're hoping to score $20,000 for it!!!

The item is the driving suit Caitlyn (then Bruce) wore during the 1982 Celebrity Toyota Grand Prix of Long Beach … a race Bruce dominated and won!!

The suit eventually came into the possession of a collector who has decided to sell now that Bruce has become Caitlyn and Caitlyn has become a cultural icon for obvious reasons.

A rep for Nate D. Sanders, the company running the auction, tells TMZ Sports the starting bid is $5,000 … but they're expecting bids to reach as high as $20k.

Hope you saved up! TMZSports.com