At the moment, European Palm Pre users cannot buy any paid apps from Palm's App Catalog but can only download free apps. However, in its Developer Blog, Palm just announced that following the launch of the e-commerce program in the U.S., the European e-commerce program is planned to go live in March 2010. The e-commerce program has about 600 new paid apps available in just 2 months, and the extension to Europe gives developers a compelling new opportunity to distribute and monetize their apps. In Europe, Palm Pre is currently available in the UK, Ireland, Spain and Germany.
Further details have to be announced but it's most likely that many of today's U.S.-only premium-apps will also become available for European webOS users. Not yet known is how Palm will handle the payments - either direct or through its carrier partner(s) in Europe.
Cheers ~ Arne