That's the annoying system, they make you pay. However, that's the price one has to pay for cheap flights.

But similarly, I hate it when other people ask me to switch seats. Please, just pay if you want to sit with your family or friends.
My flight to Japan - i had seats with my friends but because this family must be seated together, they took my seat before I arrived. The flight attendant then told me about it and I had to take the guy's seat. Fairness? None. Annoyance? Aplenty. So that's why no more AA    You can say I should have been more "understanding" to "give my seat away" but I'll say that's up to individual. Dude, that's MY seat. You should have waited for me to ARRIVE, then ask. Not sit on it and pretend nothing happened and didn't even say thank you or anything.

Yes, if they asked nicely, I will give up my seat yet no doubt I will tell them that next time please just pay a little additional to ensure you're seated together rather than taking someone else's seat.

So end of the day, please, refrain from asking others to change seats with you. Cough up that additional amount or stay in your assigned seat please. Do not make it inconvenient for other passengers. It's a tough situation because if they refuse, it may seem like they're inconsiderate.