I think 40m is a great price considering he has had 2 great years and one good year in the BL, he's generally healthy and is a great fit for Liverpool, not to mention his age. If he continues on improving and doesn't pull a Robinho, they can squeeze out at least 60m from RM/Barca in 3-4 years time. If he flops, they can get most of their money back next year. If he stays and becomes a club legend, that fee will easily be looked back as a bargain.