Value of unlicensed software <> value of lost sales due to piracy
Perhaps so. But quite a few vendors have a pretty sophisticated way of quantifying these losses.
The price per license varies by customer type (commercial, academic, government, etc), volume, license type, whether maintenance and/or support are included and for what term and type, and so on.
In large markets like the USA, the consumer segment might very significant, but in others like SA it is far less so.
It certainly used to be the case that Microsoft internally got very granular about this in order to arrive at as accurate a view as possible ... total PC shipments, PC installed base, attach rates and number of naked machines, OEM and DSP sales, etc, etc, all mapped against a very detailed segmentation by customer type, user type, industry, organisation size, etc. There is a very large amount of detailed information available from >100 countries worldwide, not just internally but from industry surveys. I think most people would be astonished to see how much effort is put into ensuring that the numbers are tested and refined so they are as realistic as possible.
Of course smaller companies might just thumb-suck a figure.
BSA members share only very broad and global figures at the BSA (members include intense competitors) and these are rolled up by the BSA itself to arrive at an overall piracy figure for a particular geography.
It might sound improbable, but BSA figures have historically been conservative and generally understated.