Talk about your price gouging! AT&T has just released their international data plan (via BGR) info for the iPad. International data roaming prices are always pretty ludicrous, and this is no exception. $25/month gets you 20 MB, $60/month gets you 50 MB, $120/month covers 100 MB, and $200/month covers 200 MB.
$1 per MB is absolutely outrageous. If at all possible, I'd suggest getting a local data plan when travelling. If you can find one that won't force you to sign a 2-year contract, that is. Thankfully, AT&T was good enough to ensure that roaming add-ons will not auto-renew every month.