The default way to order content from the Play Store is to add a credit card to Google Wallet, but if you've grown accustomed to having purchases show up on your bill like the good ol' days when phones were phones, there's the option to enable carrier billing. The choice isn't universal, and while it's available to customers on AT&T, Sprint, T-Mobile, and Verizon here in the US, it still has to trickle out to other carriers around the world. The latest addition is Orange in France, joining the likes of competitors SFR and Bouygues in the country. All three accept payment in Euros.
This is a step in the right direction, but there is still quite a ways to go before most Europeans can take advantage of the functionality, and support is even poorer elsewhere. Nevertheless, progress is progress.
Source: Google Play support
Thanks, Thomas Delattre