If you look at ratios:
Lescott 24m, Fellaini 15m (when last payment goes through). now Fellaini was definately not as good as Lescott, but lescott wasnt worth 24m either. Ratio kindof evens out.
Ronaldo 80m, Fellaini 15m. Ronaldo when at man utd was an almost perfect player (too bad he was such a [Poor language removed]). Not worth 80m, and if you were to go by that, Fellaini couldve cost 30-40 mill.
Today's players are overpriced, you can still find some for a fair value, (Vermaelen for around 10m to Arsenal), but right now in england it's all shot up to hell. So 15m for a player who did good last year, will maybe be a bit worse this year, but who will in all likelihood be a really good player in 2 or 3 years time, is nothing. We'll probably make 10m or so in the end.