[throwaway328]

I suspect you might be observing two correlates and picking one as the cause of the other in a way that is ahistorical.

Specifically, it seems to me that colleges becoming more vocational and colleges becoming more expensive are both natural outcomes of the neoliberalisation of all things. I am aware that some students now rationalise their educational investments with the logic you describe above, but I think it's a post-hoc rationalisation.

You can get a good job without going to college, and you can get a good education without paying a gazillion bucks.

A side point, but calling it "vocational" seems a bit euphemistic too. Learning carpentry is a vocation. Getting a business degree is not equivalent to learning carpentry. I might say colleges have become commercialised, rather.