What is a players value in a part exchange deal????????

[SportingPM 31]

I have recently lost out on two transfers of players from unmanaged clubs where at the moment the bid was accepted my bid was the highest when taking into account the value I could see of the players offered by another manager in part exchange. But after the transfer had gone through I saw that the unmanaged club valued the player offered in part exchange much higher, so my bid was turned down.

I then experimented with offering deals to a few unmanaged clubs with my players in part exchange. In every case the chairman of the unmanaged club valued my player at exactly the value he appears to be in my squad (Of course my chairman suddenly decides to value the player almost double the value he appears in my squad).

What is going on with players values ? Has it gone back to the old system where you can get far more for a player in PX but only in some weird semi invisible way?

Can someone please explain to me the logic for this?