That's an interesting thought. It could go either way.
It could be like Apple devices. No matter what they do they still sell those things.... It's irrational.
or
It could be more in line with typical economic curves...
Though I'm not certain that you've changed the core economic factors, the car still costs the same you've just asked for more up front.. I think, for mental experiment-sake, that orders wouldn't shrink much (< 10%) if you asked for 5k up front.... It's a limited supplier market and there is a certain amount of irrational exuberance. (It would be an interesting experiment.)
In a related economic experiment; I watched a line at Chipotle grow to over a mile long on high street in Columbus Ohio once when they were opening the Chipotle there and giving away "Free Buritos". I asked someone what was going on and they said, "FREE BURRITOS MAN!! FREE!!!!" to which I replied, but you're going to wait in line for AT LEAST 3 hours to get that burrito! To which he replied, "... but they're FREE! Totally FREE!"
Most people will consume things even if they suck, and are free and they'll generally feel great about it (Not saying chipotle burritos suck, I enjoy one now and then), and alternatively they won't walk away from and very consistently value something they pay for, even when it's very little.
I would bet, (I don't have available data) that not many folks walk away from their deposits. and not many folks would fail to order if you asked for 5K up fron You will find some, but statistically i'd wager it; would likely be very few.