Why don't the restaurants just dramatically inflate their prices to accomodate the Grubhub fee? I don't understand why it would be better to contact the restaurant directly for the restaurant -- they benefit from Grubhub too, and if they don't want to pay the cost they should just pass it on to the customers.

The restaurants have voluntarily entered into this arrangement. If they can't afford to operate with the fees on top of their regular prices, then they have to increase their prices.