Hello Mmowned,
First of all, please excuse me for the mistakes I'll surely make, I'm French. ^^'
Well, you have probably saw that Blizzard is curently selling World Of Warcraft + BC + Wotlk for only 20€ (or 20$), so what you have to do is purchase a lot of CD Key and then sell them back for 30€+ when the offer will end...
You'll earn 10 extra euros doing nothing
PS : I don't know if you can create EU accounts buying the CD keys on the US website, but if it works, you should buy the keys on the US website, it will cost 15.10€ instead of 20€