Why does HP sell an Audio Spectrum Analyser for $20K when for five bucks you can buy the software to turn your Audio Line Input Port on your PC into a Spectrum Analyser?

It all depends on your needs. Even if I was a hobbyist, I would want equipment that could do serious work... because somewhere down the line you never know you might end up with some paying work and your toy-town instruments just won't cut it. If you're playing with PICs, you want to go and be able to sample and display 10MHz logic signals at the very minimum. 200kHz bandwidth is just lame.