out of the mouths of babes

My family was traveling to Hereford last weekend and we were driving through Alamogordo when my youngest son ( 8 years old) wanted to stop and eat at Subway. I explained to him multiple times that we brought food in our cooler and that we were emphatically not stopping. After several back and forth comments I said: " Matthew, what's the difference ? You can fill your stomach with what we have already paid for or go spend money at Subway....why do you feel like we need to spend more money right now ? " He said: " But Dad, these are trained professionals ! "