An interesting present day case is the ACM charging for academic papers. Some papers are available from the author's website for free, but some are not. Although the fee is affordable (around $20-30), do publications that are free lead to better propagation and thus more/better research?
I think it's very hard to judge this, because I think what happens in practice is that unknown academics give away their papers - it helps them to get known. Whereas the ones that you have to pay for are the massively famous ones with (eg) 700+ citations. Their knowledge is already out there in the community, and their reputation probably further promotes their research much more than the small fee retards it. In addition to this, you're probably better off reading a free review/summary/interpretation of the famous work than reading it in the original - so the ideas keep promulgating.