[yummyfajitas]

Assuming you are discussing college and similar forms of education with high marginal costs (e.g. stuff involving teachers), how do you prevent society from wasting resources on unproductive education?

Of course, if you are discussing education in general, the cost is already close to $0. Khan, duolingo, wikipedia, etc are all free.

[minikites]

The devices and means to access those services are far from free.

[chroma]

Well, yummyfajitas did say, "close to $0", not free. And I think you are forgetting about libraries. They offer Internet access and they are far cheaper than colleges.

Edit: In 2011, the cost for all libraries in the US was $11.5 billion.[1] In the same year, $483 billion was spent in the US on college education.[2] That's a 42x difference. Granted, the uses and use-cases are different. But anyone who can go to college can, if they have the motivation, get the same knowledge for far cheaper.

Of course (excepting a few unusual disciplines like programming), credentials help one's career more than knowledge.

1. https://www.imls.gov/assets/1/AssetManager/FY2012%20PLS_Tabl...

2. http://nces.ed.gov/programs/digest/d12/tables/dt12_029.asp