[QUOTE=Astrosus]2900 $ for such a program seems very expensive.[/QUOTE]
You only need to buy the US$2900 professional licence if you make $100,000 or more in a year, at which point it is actually quite affordable.
I think in the longer term node-webkit will probably end up the better option, but for now Awesomium is functional -- noting that there are a few problems that may have to be handled -- and makes for a good option if you're not comfortable using node-webkit by hand.
For a browser-based game you could require that users log into your game and then authenticate account details to ensure they have paid. This often works well with a "freemium" style set-up where the basic game is free but players can pay small amounts to add additional features or capabilities to their account.