I will say this, Parallels is great. But I'm really sick and tired of paying $50 for an upgrade. Really $50??? In the long run, it's just like purchasing another laptop just to have access to my favorite Windows application. A lot of softwares don't charge for an update. Look at Mavericks, it's free upgrade. I will never purchase an upgrade again. So I guess that's it for Parallels for me because it won't even launch now on Mavericks!
The comparison with Apple is not a fair comparison, of all Apple's revenue, only 7% come from iTunes and Software, I suggest drawing a comparison with other Software companies and not an hardware company. I can suggest you some: VMWare, Adobe, Microsoft, Autodesk, Valve, and so on.
I agree with Specimen that comparing to Apple is not a fair comparison, as Apple is (now, at least), treating their OS as a free/integral part of their hardware. So they're making their money from hardware and giving you a "free" OS, with the cost of the OS effectively built into the cost of the hardware. As Specimen stated, a better comparison would be to software companies, like Adobe. Here, Parallels comes up short, however. As an example, Adobe Photoshop CS3 was released way back in April, 2007 (over 6 years ago!), yet according to this FAQ on Adobe's website it should continue to work under Mavericks. Parallels Desktop 7, however, which was just released about 2 years ago won't function at all under Mavericks.