By One, The Many Are Free

“Buy one, get four free.” Today is the Fourth of July and I’m pretty sure we’re going to see and hear a lot of fireworks going off tonight. There are tents selling fireworks up and and down the roads and in mall parking lots. One of the tents, in the parking lot of the story where I go grocery shopping, it had a sign which read, “But one, get four free.” Or course, in that case, what does it mean when they say “free”?