They didn't buy the Vettes, the leased them. NASA got bent out of shape when GM gave Allen Shephard a '62 Vette because they don't allow their 'Nauts to endorse any product, and accepting a free car might be viewed as an endorsement. So GM leased them their Vettes for $1 a year. Which NASA didn't carp about because they didn't "own" the car.
I was just passing on the info on the ?History channel?.