That's a pretty good way of summing up my views on the economics of science, although not perfect. There is a frontier in science (it's the endless frontier, after all!) so there are certainly going to be some supply constraints. Perhaps the point is that those aren't really the binding ones in most cases (and if they are binding it's probably a constraint that could easily removed in due time by a scientific demand shock).
Anyway, regarding science demand constraints:
Measuring in Listerines
52 minutes ago