I'm generally sympathetic to this perspective, but the problem is that the restaurant receives the reputation hit when GrubHub delivers late, cold, overpriced food. Customers don't understand what they're buying, and when something goes wrong, they leave bad reviews on Yelp et al.

This seems like an information problem rather than a pricing problem. As long as the customers understand the relationship between GrubHub and the restaurant, I don't see any problem with GH charging whatever the market will bear. But right now they seem to be deliberately misleading the customer by listing fake prices separate from the delivery fee.