GameMaker Studio, which is currently under development, is tentatively priced at $99 and will publish to Windows, Mac, iOS, Android, and HTML5.
This is inaccurate. Studio is $99 to publish to desktop, and $200 per additional platform, unless that has changed in the past month.
As for future pricing, the one reason why I'm not announcing the pricing today is simply because I don't want to set expectations and back out on it later - that I think everyone here can understand. If you're expecting the "full house" to break past $300, I can say that much - it's not going to pass that mark. I think that you can conjecture what the few possible price points would be based on that.
One thing to bear in mind is that Stencyl, for all intents and purposes, is a personal business and has been funded entirely out of my personal savings and done on personal time. Although the overheads of that are lower, at the same time, we dont have millions in the bank like a venture-funded company does. When you do, you have a lot more leverage to keep the prices low, and heck, if I were in that spot, I would too. I'd love to say more about this, but it would be totally inappropriate in a public forum - you're free to e-mail me, and I can talk about it further.