Double Dipping the Surplus Value

I have been thinking recently, as I often have cause to do, on the wretched state of software. This has lead me to an economic analysis of the software industry, not something I'd normally indulge in, but now that I have the vocabulary for what was annoying me, perhaps I can dwell on some other matter.

"Surplus value" is a technical term, associated with Marx but by no means discovered by him, describing how capital accumulation takes place. Horribly simplified, surplus value is the difference between the selling price of something and the labor cost, with the idea being that it's mostly unpaid labor that makes value for a business (i.e., people aren't really paid for the full value of their work). As I said, this simplification is gross, but it's the basic idea, no great surprise nor particularly radical.

Whatever you feel is the correct relationship between labor and the pay for that labor, it seems to me that software companies who produce crappy software (that is, most of them) rely on not one but two sources of surplus value, first from their own employees, second from the poor shlubs who buy their software and then have to hire even more IT staff. How much of that expensive software companies are convinced buy would get any use if there weren't an army of acolytes running around tending to it?

What percent of the average IT budget (training and salaries) is devoted to necessary infrastructure and what percent to dealing with software that doesn't quite work as advertized?