You will need to run OSX and Xcode to develop for iOS. However you don't need to buy a Mac.
You can create a Hackintosh (possibly using your current machine.)
See http://www.tonymacx86.com/ for help on doing this.
It can be a bit involved, but it is much less costly than buying a real Mac. I have a PC that can dual-boot into OSX 10.9.2 and Win 8.1 and it works perfectly for developing Cocos2d-x apps for Mac, iOs, Android, Win32, WinRT and WP8.