Somebody that doesn't want to spend $200 on a product with a complete-satisfaction guarantee probably won't be a very good long-term customer. The RubyMotion guys are filtering out the low-end of the market, which from a business perspective, is a good move.
Besides, every crappy product advertised on TV ever offers a "money back guarantee", and some cursory googling should show that those often aren't worth the electrons used to transmit the image to the screen.
This is the internet age, and we're talking about software. You get paid after I see what you're selling, and not before. Code samples and writeups are nice, but it's no substitute for getting one's hands on the tool.
I'd also like to call out the rather annoying trend of any criticism of pricing being met with the "keeping out the low end market" dismissal. Sometimes, your product is just overpriced and your sales methods leave a lot to be desired.
Many developers have no problem whatsoever spending $200 on a tool like rubymotion, in fact I think it's a bargain. A money back guarantee is a bonus, and no-one has any reasonable doubt as to its legitimacy. I agree completely with the GP that this makes good business sense.
I do not. But apparently personal principles are unwelcome here.
If excellent customer reviews and a real money-back guarantee don't convince you, then I'm not sure a free trial will either.