For me they are always good buys.
My first one is still in the Team, plays as MC and is average is 0,5 goals/game witch for a player in His position is very good.
The second, got injured 4 times, 3 in the same season, i put it on sale, and end in a bid war, so a goo income to me.
The third is now my 2nd GK, and he is playing very well, Everytime i need him.
Still waiting for them this season, just need to upgrade the youth academy in the right time, to get them earlier in the season.