WordPress (com) introduces so called “premium themes” which is just a synonym for that there is a theme-market now. Founder of Automattic – the company running WordPress.com – Matt Mullenweg blogged about this as well.
Looks pretty quickly hacked in, prices aren’t displayed when you are not logged in, as can be seen on the entry of the Headlines theme in the Theme Showcase, one of the two first themes with a price-tag.
The Theme Showcase was announced about one and a half month ago. It’s where the market is now located.
The marketplace idea is years older, but Automattic had problems to get it running back in those days.