> Plus, last time I checked you need to pay to be able to have proper access to all developer information
You checked wrong. Developer docs for production versions of Mac OS and iOS are all available for free with Xcode. You only need to pay for membership to the developer program, which gets you access to prerelease OSes (and related documentation), and lets you distribute your applications through the App Stores.
Mac cost perhaps a grand five years ago, still running fine. So about $200 a year. Meanwhile cheaper laptops I have used die a quicker death as they are not built as well, apparently. So my guess is that they are roughly equivalent.
All commercial UNIX vendors sell their compilers. Even in Solaris case, the EULA does not allow you to sell software done with their "free" compiler.
Intel compilers are not free for Mac OS X and Windows.
All the SDKs for game development from the console owners are not free.
The express editions of Visual Studio compilers are limited in which optimizations they offer, libraries and supported processor targets.
The compilers from Portland group for HPC.
The compilers from CodePlay for the game industry.
Even the compilers from Apple can be said that they are not free, after all you're paying indirectly for them when you buy a Mac Developer's license.