Couldnt they though? A medium fry at mcdonalds costs about $4 and you can buy 5lbs if potatoes for $4.

I think its more like 40 cents to make at home. So I think its quite unlike McDonalds.

How much does a fryer cost? How much does the fryer cost to run? How much would it cost to get the fries into the customers hand (i.e. food truck, rent)?

A single person could make french fries for themselves cheaper than McDonalds, but once they have to start including the cost of the building and equipment, charging for their labor, and complying with health codes and worker safety requirements, they will quickly find that the fixed costs swamp the variable costs.

(numbers are just to illustrate a point, not accurate) Now assume you can't buy a 5lb bag of potatoes and you can only buy 10,000 lb bag. Now also assume that you can't buy this 10,000 lb bag unless you know someone else will pay for fries for the other 9,995 lb because you can't eat that many fries. That's the kind of scale the token inference market is efficient at.