Modern Mac Development?

CDarklock asks: "I'm getting seriously interested in setting a new Mac next to my Windows box (to replace the Mac SE, which should tell you about how long it's been). But on Linux and Windows, I'm accustomed to writing lots of custom apps in C++ to fill the gaps around the system, but I haven't written anything on a Mac for something like fifteen years. As a professional Windows developer, what sort of expense am I facing to outfit a new Mac with development tools comparable to Microsoft's Visual Studio .NET, and what sort of learning curve should I expect?"