MaxRoam has a solution for the ruinously high price of using cellular data on a 3G iPad outside the country in which you've signed up for service. Its Euro iPad Pack is a micro-SIM that can be inserted into the 3G iPad and allows flat per-megabyte roaming with no expiration across Europe. The micro-SIM ships 1 June 2010. (Japan is, so far, the only country in which Apple is locking the 3G iPad to a particular carrier.)
The MaxRoam micro-SIM costs €75 (about US$95) initially for both the SIM and 50 MB of data. Additional data can be purchased in either 10 MB units for €25 (US$32) or 50 MB units for €75. The company provides scant information, but it appears that data does not expire at the end of a billing cycle, since you buy data in chunks as you need it.
AT&T's 3G iPad international service plans - which work across all of Europe, too - cost $24.99 for 20 MB, $59.99 for 50 MB, $119.99 for 100 MB, and $199.99 for 200 MB; data must be used within 30 days or it expires.
In other words, like AT&T's unique unlimited 3G service plan in the United States, AT&T's international service plans are far cheaper than this competitive European alternative unless you're worried about data expiration.
I haven't yet seen any information about pan-European roaming from European carriers, but I wonder if MaxRoam will be competitive there as well. The European Commission's Telecoms Commissioner has been aggressive in forcing carriers to lower voice, text, and data rates across EU borders. If AT&T can charge $60 for 50 MB, I'll be curious to see whether Orange, O2, Vodafone, and others can beat that deal.
Of course, all these roaming prices are essentially international highway robbery. Providing data costs the same on a modern cell network (2G and 3G) whether or not the user is a customer of the carrier or of a roaming partner.
The big cost is billing, in which carriers need to settle roaming charges with other carriers, but that should, at most, add 10 or 20 percent to the normal cost, which already includes a substantial profit margin. The markup is even more ridiculous for carriers - like O2, Orange, and Vodafone - that operate networks in multiple countries. Those firms are moving billings around among bank accounts owned by the same multinational parent, and have even fewer costs.
What drives international roaming prices for voice and 3G data is monopoly control. While countries can do something about pricing among carriers within a nation, there's little regulatory control that forces a European or Asian carrier to give AT&T a good roaming price, nor - if AT&T is paying a far lower cost than it bills - to force AT&T to charge less. Within the EU itself, though, regulators have that power, and have pushed through lower prices by the force of law and the force of shame.