How about demand scarcity verses supply scarcity? The classic argument is that proprietary software uses artificial scarcity to maintain high prices. To fund the development of software with limited demand projected prices must be set high enough to justify the cost of building it.
True the bits don't cost anything and copying is unlimited but resources to develop don't become unlimited as well.
That's correct. Therefore a funding model for software without introducing artificial scarcity relies, as I see it, on directly funding those development resources. E.g., I've been working on the Free Pascal Compiler (FPC) as a hobby project since 1997, but the last couple of years I've been approached by several companies to implement certain features and extensions to it, and I've done so from time to time on a self-employed basis. Another funding model that's been making inroads lately is crowdfunding.
Note that I'm not saying that these models are easier than one whereby you introduce artificial scarcity, especially if you have a general end-user or business application as opposed to a fairly niche developer tool like FPC. More scarcity at a similar level of demand = more income, that's an economic given. However, as a result I don't think there is anything wrong with the statement that selling proprietary software licenses is an economic model based on introducing artificial scarcity (maybe as a proxy for a real scarcity, but possibly in a way that values this first scarcity higher than its "intrinsic worth" -- similarly to how monopolies result in higher prices).