We’ve probably offered him around £250k a week and due to what we are paying others he’s wanting >£350k a week.
I don’t think there is a side in the world that would pay more than what we are offering him if a transfer fee is involved, but if he were to run his contract down and leave on a free...
He should get parity with our highest earners and if we aren’t offering that then I can understand his refusal.
He shouldn't get parity with Sanchez, because that contract for Sanchez was a big mistake. Assuming that he plays as many games as are weeks in a year, he is really getting close to 500k/week, which puts him on top 5 most payed players (after Messi, Neymar, Ronaldo and Bale), but he was nowhere near a top 5 player back then (now he isn't even a player, based only on United's career). We cannot fix that mistake by increasing the salaries of all other players we have.
Saying that, De Gea is clearly our best performing player, so he should get a nice bump on his contract, which puts him around current Pogba's wages. Even a bump of just 50k/week, would put him at 250k/week which would be double of the next best payed keeper in the world, Manuel Neuer (Courtuis might be on more on Madrid, but couldn't find the numbers). Considering the special case we are on (Sanchez mistake, De Gea being our best player, the mess we are on), we should consider a 250-300k/week salary, which for a keeper is an insane amount of money, and quite unlikely that is going to be matched from any other club, unless PSG goes batshit crazy. If PSG goes batshit crazy, then offer to De Gea whatever he wants.