I just bought my first Mac (widescreen iMac) and it came with Jaguar so I can't really address the upgrade cost. However, I've been a Linux user for 9 years and it was OS X that convinced me that a Mac was for me. I've had one instance so far where I had to boot into OS 9 and I hope it's the last.
This is my first Mac and if Apple abandons OS X it'll be my last.
BTW.. I wrote code for a little high-tech startup on Mac SE running System 6 many years ago, so this wasn't my first experience with Macs.