I think the starting point of that could be more precisely identified as "the fewer buyers for a given piece of software..." the more expensive it is to own.
If you're the only customer running OS/2-on-NT-using-Token-Ring-over-Carrier-Pidgeon, you're not going to have a good time when you find a bug or missing feature.
If you're the only customer running OS/2-on-NT-using-Token-Ring-over-Carrier-Pidgeon, you're not going to have a good time when you find a bug or missing feature.