!!! UPDATE BELOW !!!You're right.
Anyway, if we look at the only legit way of "buying" ISK for IRL money in EVE: The Game Time Cards
It costs you around $15 to get a 30 day GTC, which sells for around 150m ISK on the official EVE Online forums.
If you would buy 1 billion ISK with GTC's using $USD it would cost you 6,66 30 day GTC's, which is $99,9.
So let's say 2,5 FG per million since I'm a nice guy.

So that's 625 FG for 250m ISK. Sounds better?
Thanks for your input munkyman, I hadn't really calculated and only went for what others were trying to sell ISK for and undercutting a little. Will edit my original post as well.
Edit: Apparently you can't edit the orignal post, how unfortunate... Oh, well. I hope people are reading this as well.
This post was edited by qurbitz on May 13 2008 08:45pm