Hello Echino,
I don't think its crazy to negotiate a salary that will put you where you want to be financial. If they need your talent to fill a spot they will take it seriously. There are a lot of points to be taken into account when considering moving to another country. Too many to list here but keep in mind that salary is only one. Companies making offers to attract talent and knowledge that they cannot find are willing to accept that they must pay for it. If you offer is to high, they will let you know. Then again, they might accept it without question. Would't that be an eye opener. I've been working outside my country (USA) for over thirty years and enjoy it. Go for the high salary!
Best Regards
Mike Silvia