Jones and Rojo won't get much but they should go.
Schneiderlin only if Mourinho genuinely can't see a future for him and even then, £20million minimum.
Darmian is weird one. I haven't seen a match with him all season (has he played?). I wouldn't be hasty to sell him myself but what do I know.
Memphis is another weird one. I'd personally just sell/release Young and let Memphis take his place. Might as well get rid of one 'waste of skin' player and use the other who might graduate to a good player eventually.
Think you're looking at £30-40million at best.
Again, depends on who we're selling them to. If we are selling Schneiderlin within Premiership (I think there will be buyers) then £15m is a realistic price. Not sure if any club is going to go above £20m, he has barely played any serious football for over a year and his stock has gone down.
Darmian will not find a team for him within England unless it's Watford or something. He's much more likely to go to a good club in Italy - Inter, Roma and Juventus have all been linked. None of them will go much above £5m, they usually consider signing these flops as bargains. Zlatan cost £18m when he moved to Milan.
Depay has also been linked with Italian clubs mostly, his reputation within England is not very good and I don't think many teams will take a gamble on him, especially at larger prices. Maybe £15m tops. I wouldn't give up on him just yet but if Mourinho does not feel that he can contribute, then there's zero point waiting. Letting Young go instead could be good if we can find playing time for Depay but then again Young can cover 2 or 3 positions and is competent at full back which Depay will never be.
Rojo is a bit crap but someone will still pay £5m or so. He's Argentina international. Jones we might need to let go for next to nothing, he's hardly ever fit and most don't remember that he even exists. He will obviously be fit all the time wherever he goes and will never miss a game.