Every player has his price and every player should be sold for that price, end of!
Unless we're winning every single game and have the XI best players in the world, until then we have to trade and find a way to improve.
Whether that's by finding lower-priced gems such as Arteta, Cahill, Lescott, Stones, Jagielka (funnily enough all Moyes' purchases) or by selling for way over value and using that money to bridge other areas of the squad that need improving - it must be done.
Right now we're the 11th best team in the league, which shows we have a LOT of improving to do.
Martinez cannot be trusted to get the majority of his 'small' buys right as Moyes could. Yes he got McCarthy, yes he got Lukaku, but they are the big money deals where most people knew they'd be good transfers. But he also made far more awful transfers and refused to get rid of the players, allowing them to be a huge drain on resources. Those tranfers that looked like a gamble at the time have, pretty much without exception, not paid off.
IF Chelsea come back with 30/35m, and IF that money goes to the manager then he should and will go. We'll end up a better team for it, as it allows Martinez to buy players who'll be less of a risk and more proven.
We could get a second good striker, a class centre back and a top quality number 10, and furthermore push players such as Kone, Naismith, McGeady further away from the starting line up.