Regarding pricing: I wish we could price it much lower but the reality is that this tool is extremely niche. We've also put a _huge_ amount of work into it and I hope it shows in the amount of polish (although there are many more things we would like to improve and add but we had to call v1 at some point). If we ever stand a chance to continue making the best software we can, we have to price it in such a way that will allow us to do that. Note that we might still fail and not achieve a sustainable level but if we priced it at, say, $30 or $20 then we would definitely not be able to continue making the apps we want.
Regarding 10.9+ requirement: we do depend on the improvements in AppKit in 10.9 regarding layer-backed views and hence the requirement.
Hope that clarifies both issues.