Huh?

Does this make sense to you?
I took the team to King pie and our order included 17 pies. There was only one chicken pie.
“I have 12 more in the back.” The man at the counter said.
“Great.” said the pastor. “I’ll take those 12, and then that one makes 13….”
“No, I can’t sell you that one.”
“Why not?”
“Well, what is someone else comes in and wants a chicken pie?”
I don’t get it.
But is wasn’t just at King Pie. The pastor tried to buy several purses for his wife, sister, and mother. But he was only allowed to buy 2, because they were trying to save up their inventory for a trade show this weekend.
So, I guess the idea is to pass up a definite sale today for the possibility of a sale in the future.