@Bojanbbz94 You're adding way too much real life stuff into this game mechanic issue. The EPL has a much higher wage budget than the Danish Superliga, therefore SI has made it so that especially highly gifted players will demand more when those clubs come knocking. It matters very little what they're currently earning.
After the negotiation fails, the player resets and now re-evaluates his options. FCK may then be the best of the rest and he'll demand an outrageous amount of money from them, relative to what they're already paying (much less than the EPL club offered because they're no longer a factor).
On a side note potentially playing Champions League with FCK is much more attractive than U18/U21 matches for Everton, Southampton or West Ham. In general the EPL is infamous for being a bad place for young players looking to develop into first team players.