score:2
For non-LCC flights, usually gate checked luggage is free, especially if the gate crew or flight crew force you to do it. This is often because the gate crew is incentivized to board the plane quickly so that the flight isn’t delayed. And unlike the ticket counter crew, there’s little monitoring of their revenue generation.
Some people do deliberately take advantage of this revenue loophole but I’d rather them do it this way than hauling their huge bags onboard.
LCCs are much stricter. I don’t have as much experience with them so I’ll leave it to another person to respond with an LCC-based answer.