So those really are one-spoke spaces? (I thought that maybe the $500s signified that you'd earn $500 per letter while collecting half a car, or something.) I'm a little surprised -- that's twice the work required to win the old $10,000 prize, with only a slightly larger payoff.
If my math is right, it's more work than winning the million.
To win the car:
1/72 to capture 1st wedge.
1/72 to capture 2nd wedge.
Solve the puzzle before hitting bankrupt.
Profit.
To win the million:
1/72 to capture the wedge.
Solve the puzzle before hitting bankrupt.
Win the game before hitting bankrupt.
1/24 to capture the million envelope.
Solve the puzzle.
Profit.
So although you have one less puzzle to solve for the car, it's still knocking on the door in terms of difficulty.