(and was unsurpisingly done by a Golden-Road regular who knew where the producers would hide the car and master key)
Huh?
It's another one of those psychological tricks that producers can use to influence whether a game is won or lost. Humans, when presented with a set of five otherwise-identical options (keys in this case), will pick one of the middle options far more often than the outside two. Checking the TPiR stats page, over the last 20 years, contestants have selected key #1 only 11% of the time and key #5 16% of the time.
The producers know this, and in order to save on the budget, often put the car and master key in those positions to "hide" them. Out of the 21 times Key #1 was selected (and used), it unlocked the car lock **17** of them. Likewise, Key #5 won the car 20 of the 32 times it was selected.
So, obviously, if a contestant were actually to get on The Price is Right and play Master Key, it would be very much in their interest to take key #1 (and #5 to a lesser extent), but who outside of this little corner of game show fandom would even think to look for a pattern there?
TL;DR: If the keys were assigned randomly, each one would win the car 40% of the time, but they're not, and Key #1 wins the car over 80% of the time, though nobody outside of g-r would realize it