55 is a crazy figure I wouldn't pay any more than 40 but I don't think it's an obligation. I'm expecting us to negotiate a better price depending how well he plays this year and I imagine alot of the 55 would be bonuses.
Seen 34 year old Dzeko being rumoured to cost between 15 and 20 million euro. Where the fuck are they getting them figures from? At that age there shouldn't even be a transfer fee.
There's no guarantee that any player from Lazio or Inzaghi will be as good anywhere else. They are great as a team but we've seen this many times over the years and when players/managers leave they are back to being average.