I wouldn't take the offer very seriously. A search for "playfon" on the Russian Google yields a top result of Playfon's cheap dating site (nsfw images) for phones. That's their top result. Not their main corporate page, or any other relevant information.
They appear to be a legitimate company, but they have little to show in the smartphone market. Their portal system is designed for platforms without a centralized marketplace, and frankly, I'd expect the Android Marketplace to perform far better on Android devices, even in Russia. Since they also want an APK that can install off the marketplace, you're going to lose that mode of security, and you'll have to trust that they pay you the right amount.