Well, economic returns have to originate from somewhere. Either your additional education allows you to take something away from someone else our it allows you

Well, economic returns have to originate from somewhere. Either your additional education allows you to take something away from someone else our it allows you to increase productivity and reap its benefits. Also if you spend five additional years at university out of say fifty working years, then you already have to increase productivity by ten percent only to match your economic output without spending this additional five years studying. And in highly competitive markets, that are already optimized to death, ten percent is a lot and even then you just broke even.