No definition of a "win" is going to perfectly fit all 77 pricing games. To the home audience and contestants, it makes absolutely no difference $20,000 in Plinko or $18,000 in Time is Money is just a "partial win" or even a "loss" in the official or semi-official record books. They don't feel like losses, the contestant wins something big and is happy, and that's the important part. It's presented as a victory.
But if we're absolutely forced to make one set of rules for all pricing games that determines whether it is a "win" or a "loss", I suppose we have to treat it as a cash game. I just pulled up Drew's explanation of the game, and this is how it was presented:
Drew: "Irene, it's your birthday. We have to have something nice behind that door. I bet this is exactly what you want for your birthday."
George: "You bet, you got a chance to win $10,000 in cash! Playing Half Off!"
Drew: "Yes, we have 16 boxes. One of those is stuffed with $10,000 cash. Your job is to pick the box stuffed with cash."
Boom. Right there, he says the object of the game is still to pick the one stuffed with cash. The "big prize" behind the door is the $10,000 cash. It's the first, big thing the contestant sees. Drew even uses the exact words "your job is to pick the box stuffed with cash". If she does not pick the box stuffed with cash, it's not a win.
Then Drew continues with the rule explanation:
"...and you can eliminate half the boxes until you're down to two boxes, and I hope you do get down to two. Because it's Dream Car week, we have a little extra something to give away."
George: "We do. It's your brand new car!"
The car was presented as a bonus prize. According to Drew's explanation, the car seems like a consolation for "not" getting the cash. Despite the fact the contestant would clearly be thrilled to win either one, winning the car would be like winning the second prize in Any Number. Not a full loss, but not the big prize that you're supposed to be aiming for.
If we're hell-bent on making one set of rules apply to all 77 pricing games, and we're never making exceptions for special playings, then winning the car would be a partial win (or, if we absolutely have to measure it as either a win or loss, it would be a loss, like winning the #2 prize in Any Number)
But I don't think the contestant or the home audience would care that it was technically a "loss", and pretty much any contestant would be happy to "lose" the game in that fashion.