AWS also recently ended support for Mysql 5, so if you had an RDS instance with that version running past the cutoff, your support costs ballooned exorbitantly.
Seems like I'm a lucky one. Neither using RDS nor MySQL. But seriously, ouch. I mean, I get why they want people to migrate to supported versions but ...
I wish we could implement this internally via chargebacks. The teams that refuse to upgrade their stuff should be forced to pay for the externalities they cause.