Think Tim was talking about the salaries of the young players, which is a fair point. However, Chelsea buy the players and immediately loan them out, so I reckon the loaning clubs are paying the players' wages.
Personally, I find it immoral to sign players with no intention to ever have them playing for the club. I think it is wrong to use young players as mere commodities that are there to make money for the club, in order to let the club sign players they actually want. That this phenomenon is within the rules is one thing, and I really hope they change the rules to prevent this, but to say it is not immoral is a bit rich IMO.