Of course it does happen, it's not a rare case, it's the usual case. Any remotely successful product will have N = millions of users. The only reason this doesn't enter the calculation is that you don't get the money you saved by not making your users do unnecessary hardware upgrades.
Ah! So there's the key point: do your users run your software or do you, on your servers? If the former, yes, it's an externalized cost and may not enter your economic calculations. If the latter, you care a lot :-)
