You voiced the idea first
I personally would rather it just be a dream car in addition to the $25,000 (or in 1/2 off's case $10,000). Make it a true bonus, vs. this way. But that's just me.
On paper, ending the game with the price reveal could work. A ton of games have their big reveal being a simple card being flipped over or a price revealed.
The only issue is it makes the prop the game is built around an afterthought. It's still a game "show"; if the game is visually designed around a giant prop with a big, visually interesting reveal, the viewer going to be disappointed on some level if they use don't use that prop, even if the contestant wins big.
Some criticize games like Half Off and Secret X because there's still a way to lose even if you price everything perfectly. But they kind of have to do it that way, cause the focus in those games is on the Secret X or the boxes with money in them, instead of the small prizes. Hypothetically they could offer a 4th X or 4th set of SPs so perfect pricing guarantees a winner, but those situations would make the big props totally moot and the big visual reveal irrelevant.
Bonus Game's "light up the bonus" is a very simple reveal so it doesn't lose as much if the host builds the game up to flipping the final price reveal card instead of lighting up the window, but there's a reason Shell Game doesn't do the same thing.