@wastingtimewithforums: The cost of running a simple website to promote your app is borderline insignificant compared with the costs associated with setting up the infrastructure to handle payments securely, dealing with customer complaints, preventing piracy and many of the other services that a sales infrastructure needs.
Not to mention the significant benefits that come from selling in a 'store' that customers have already built up a trusted relationship with. Plenty of people wouldn't think twice about buying a cheap application from Amazon, for example, but would be very hesitant to buy that same application direct from some website they just happened to find in Google. And such a store is more likely to be a go-to place for many people than anywhere else. There's a reason most business, even online, goes through stores like Amazon, eBay, iTunes and now the Windows Store rather than companies selling direct-to-consumer through their own website - it's been demonstrated over and over to be a more effective strategy.
But, as evildictator points out, if it offends you that much you can always try the freemium approach instead. Then you get to sell through the Windows Store and never have to hand a single cent over to Microsoft if you really don't want to. Or stick to desktop applications.