Think about that. I believe Mac computers as an industry had more sales last year than the entire VCR and Video industry combined. Apple gets profits on each sale. Macintosh is an industry by itself - but the Mac can share the resources of the rest of the PC industry by using the same expansion cards, monitors, printers, scanners, Memory, hard drives, keyboards, mice, cables, speakers, manufacturing, and so on. This is allowing the Mac market to grow immensely.
Market share is a measurement of unit sales at any given time.
Furthermore every Macintosh event has more attendance over the previous ones. That is what I call a thriving industry. There are over 15,000 Macintosh Applications available - so Software availability is not exactly at issue with Macs either. But remember, this market is very volatile and it is nearly impossible to predict what will happen in the next 3 - 5 years. Macs have the lowest support costs, and are the easiest machines to maintain and install.