Warning: I flew a budget airline with no carry-on and paid $65 at the gate for a bag that fit under my seat
I picked the $48 Spirit fare over the $95 Southwest one for a quick Denver trip, thinking I could sneak my backpack on for free. They measured it at the gate, and that $65 fee ate the whole savings, so now I want to hear if anyone has actually beaten the personal item sizer.
Did you even try stuffing it in the sizer before you got to the gate? I got burned the same way on a Frontier flight last spring, $59 fare to Phoenix, then $79 at the gate because my bag was about an inch too tall for that stupid metal frame. The trick I keep hearing is wearing a vest with a million pockets and stuffing your clothes in it, but I have never had the guts to try it with a gate agent watching. At this point I just pay for the carry-on up front and stop pretending I beat the system, because those fees always catch up with you.