While the data shows that wages stagnated through the rise of post-secondary schooling, proving that time has not been sold at a higher rate, there is some underlying merit to your theory...

Cars being the prime example. Wages were not stagnant through the rise of the automobile. People were able to sell their time at a higher rate by being able to travel further to where the higher paying work was found. Wage gains only started to taper off once car ownership reached critical mass, providing no additional market advantage.

So, yes, you are quite right that most people buy a car because it is the vehicle that gets to higher paying work, justifying the high cost of ownership. However, that is separate to our discussion about recouping the cost when you sell it. Both a degree and a car depreciate, but the degree dramatically faster.