I'm sure, as stated already, that the OP means thighs rather than wings.
I'm also sure that when I was in the US and visited a Popeyes Chicken, that you could select the type of chicken you wanted and it was priced accordingly.
As such a 3 piece breast meal would be more expensive than a 3 piece thigh meal. You could also combine, so for example a 1 breast, 2 thigh meal would probably cost somewhere in between the first two examples.
In fairness though, it does seem a bit much and makes the menu and ordering process a lot more complex (more questions at the order point, more time wasted etc)