Actually you can publish to the Windows 8 store for free. I had a partner who was a technology evangelist for Microsoft and he said that they paid companies like Scirra or Unity to make their exporting options free. I actually uploaded my first app when I just began using the free edition of Construct 2. Later, I bought the license so I could also upload to Android and IOS. Anyways, I do recommend buying the licensed version just because once you do, the opportunities are endless.