There were high hopes for Chelsea and Sterling when they paid £47.5 million to buy him from Manchester City. They signed him on a long contract at £325,000 per week but he was dropped from the first team during the pre-season when Enzo Maresca was appointed. Sterling had another 18 months remaining on his contract therefore it was worth around £25 million. The exact amount that was paid to Sterling to mutually cancel the contract remains unknown.
Regarding Mudryk, if I understand the situation correctly he is on a provisional ban. Once there is a full hearing he could be banned for a maximum of four years. It is very difficult to see him return to the Chelsea first team.
Chelsea have/had loads of players who are unmovable like Mudryk, Sterling, even the Saudi Pro league can't take all of them and a lot of these players cannot be disposed of without terminating their contracts which is also costly. So it's like the whole resale-value gimmick is nullified.