> It's my understanding that universities pay significant amounts for site
> licenses and that general public purchases do not subsidize that access.
Yeah, I am pretty baffled with how non-institutional users are requested to pay for access, both on JSTOR and other publisher's sites. Surely this is not a large source of income? arXiv (always pointed out as a shining example of something going right) has recently started requesting membership fees to be paid by the top 200 institutional users. Other than that, the public is still able to go to the site and read about dark matter and substring bananas.
You know, what probably happened was that when the content was starting to get digitized, the publishers only had users that were accessing from universities. So they charged the universities just like they previously did for subscriptions to the bound book issues. At the time, there was probably no concept of doing any sort of analytics to figure out where downloads were coming from, so they didn't think that maybe they should just allow anyone to download, and then setup a deal with colleges to pay their fair share. I think the arXiv model is worth some more investigation..
(This ignores all the actual truths like, they have to maximize shareholder value, they have to make as much money as possible, their incentives are aligned differently, etc. Instead it is simply focusing on the reason why "individual purchase" is an option that doesn't seem to make sense to non-institutional members like the general public.)