Unusual order

[rebbonk]

A customer walks into a restaurant and notices a large sign on the wall:

$500 IF WE FAIL TO FILL YOUR ORDER!

When his waitress arrives, he orders elephant dung on rye.

She calmly writes down his order and walks into the kitchen where all hell breaks loose!

The restaurant owner comes storming out of the kitchen. He runs up to the customer's table, slaps five $100 bills down on it and says, -

"You got me that time buddy, but I want you to know

Spoiler:

that's the first time in ten years we've been out of rye bread!"