When to lay it down?

[SideCash]

I'm probably not being clear. This is what I mean. These numbers are purley made up.

if I raise $5 preflop with AK and my stack is $15. Flop comes QT4. I bet $10, and oppenent pushes all in. Easy call right? Only $5 more bucks to call at a $25 pot.

But if I have $500 and raise $5 with AK. Same flop and same bet and someone with $500 moves all in on the flop easy laydown right?

But what about those gray areas. Say I had another $20 or $30 left in my stack when he pushes. Is there a formula of some sort that says when you should call, EVEN WHEN YOU THINK YOU ARE BEAT, just because you are pot commited. How do you calculate the close ones?