Hmm, look, I don't really buy into this "Cavani is shit" stuff, I'd take him, I think we'd all be over the moon if we actually signed him. In the case of Giroud, it would put a player already pretty much at his peak on notice.
I just wouldn't be particularly comfortable about breaking the bank for Cavani.
The performances in France aren't even as significant as the decision to move to play in France. It's hard to take players that do that for the money seriously, since as the many comments in this thread recognise, Ligue 1 is not a strong league.