Analogy is flawed.

The meal uses food that is gone after being eaten and thus can't be resold.

A digital copy doesnt change the ability of a vendor to sell copies.

A better analogy to what OP has suggested is where a cart/restaurant offers a single bite "taster" for free to try to lure you to buy.

EDIT

"Food that is gone after being cooked" should be "Food that can't be resold after being cooked even if not eaten"

Point being a costly physical thing has been used up. Unlike a digital copy.