All Greek to me... BUT
Nick, I'd be very careful with the whole purchase at the present time where the currency and whole Greek financial set-up is highly unstable. While I do not want to rain on your parade your agent should be able to quote you chapter and verse about where this fee comes from. My ritmetic is shaky but I vaguely remember an equation where a used car salesman is equivalent to a used boat salesman. It's not Greek but I do recall caveat emptor from my Latin class.
IMHO it may be better to have a reliable 3rd party in the deal that can confirm all is on the up and up, as well as the legitimacy of this fee. With a bankrupt Greek gov't a surtax a la Cyprus on large amounts, or something similar, may well be waiting in the wings there as well.
Good luck and I hope it all works out OK for you.
Ivo s/v Linnupesa