It's the Least I Could Do

But what's the most you could do? It's the least that I can do.  It's a saying we use when we've done something for someone after they've done something pretty nice for us. But have you ever really thought about what it means? It's the least that you can do? Is our least good enough? Is it ever good enough? Do I really want to do the least I can do in payment to those who gave all that