I have 12 players with 95 overall.
I think players with higher overall grew faster on stats. When you buy a player with very high stats he doesn´t have to grew very much in stats, so his overall is lesser.
In my team i have buyed 17 players for less than 1000 credits, only three cost me more than 1000:
Midfielder cost me 2700 has 95 overall
Midfielder cost me 2100 has 93 overall
Defender cost me 3000 has 92 overall
So, my best players aren´t the most expensive, and the ones with higher stats.
Most of my players that cost me 500 credits, were lower on stats, and they need to grew faster.
Not sure if its because of this.