If you win the Title your players valuation dramatically increases.
Also, I get a bug on FM 14 where the game secretly changes the currency at the end of every season. So when you go into preferences, it says that it is UK Pounds, and on my squad list it says UK Pounds on their valuation, but the game is actually using US Dollars (so their valuations jump up dramatically). SO in prefeerences change you currency to anything and save changes, then re-open preferences and change back to UK Pounds (or whatever your original currency was) and save changes. Your valuations should then be all back to normal.