Oh noes, some are even doing it with computers?!?!
If the bikes you’re referring to are cheap to begin with (or even from the trash) then the people who are flipping them are likely people who are making them rideable and better as a result. Nobody is forced to buy anything.
There’s also no reason that you can’t go snap up one of these inexpensive bikes before this rapacious predator baby boomer snatches it for his heartless capitalistic scheme; you’re just not looking or acting quickly enough.