1) You don't need Parallels: http://xamarin.com/ have a lovely ide for OS X built on Mono (open source. NET), I much prefer this to VS-in-Parallels although I'm on a lowly macbook air with 4gb of ram. There's also free alternatives to Parallels, and Microsoft certainly don't "require" it for .NET development.

2) There are cheaper windows licenses

3) There is a free version of Visual Studio: http://www.microsoft.com/visualstudio/eng/products/visual-st...

4) Resharper is great but it's a luxury and an optional one

You can use visual studios express for free. It may not have all the bells and whistles of the full blown VS it works pretty well.