How much dough would you cough up to own a piece of the biggest boneheaded play of 2018??
For one fan, the magic number is a whoppin' $23,548!! ... 'cause that's what J.R. Smith's NBA Finals Game 1 jersey sold for Thursday night ... TMZ Sports has learned.
ICYMI -- the bidding started at $620 ... but things started heating up on the final day of bidding, with the number reaching around $11k ... then DOUBLING before the auction closed.
To put things in perspective, LeBron James' Game 1 threads -- which he wore during his historic 51-point performance -- fetched $100,322 ... but that was probably bought for different reasons.
No word on the identity of the person who snatched up the J.R. jersey -- but we're guessing only a Warriors fan would want this memento.