For me that is easy. If used for personal use, make it free (and thus, more popular plus free bug reporting for bleeding edge versions). If used for commercial purposes, not free. Then go after businesses that use unlicensed copies of the software.
I can't speak for Microsoft, but I could imagine some type of negotiation on pricing based on several criteria. When businesses purchase licensing for such things, there is always a negotiation phase that starts around 60% discount and goes up or down based on many factors.
How do you draw the line between "if you weren't going to pay anyways" and "well we don't have to pay, so we ain't gonna"?