There are prolly more players that would buy him for 100k. So you would have competition and therefore he still costs more. If they introduce skill drop for every player release, we would get an affordable player soon, or get him to a range when he is not really desirable any more.
Why shouldn't there be a max salary?
Because it would create an unfair advantage to the top teams with good funds. How can a C with +5 in inside skills (all other skills are equal) cost the same.
If there are enough of these players on the market then you might get a player for 100k. I'd even spend up to 300k or something if required. Still better than paying the salary. Taking skill pops of every single player that exists every time a player is sold is ludicrous and should never happen. It would kill this game.
I don't see how it creates an unfair advantage to the top teams with good funds. Everyone in your league is approximately the same, so no one in your league has an advantage over you.
And a Center with +5 in inside skills will not cost the same. The salary will be the same, but the cost to buy the player will be double, or even triple the price.
It also provides a much greater incentive to keep training players. If I trained a player well he could hit the 200k salary mark before he is 23 years old. But why should I have to stop training now? He still has 2 or 3 decent seasons of training left in him. But at this point any extra training is reducing his value on the transfer market so teams won't do it. This isn't how it should be.