.org domains have a greater purpose, these domains allow organizations to get a better position regarding their branding and communication, which is very important for most non-profits. Price increases can be reasonable as long as they are coming along with better services, like entity verification or anti-spam measures that help prevent bogus non-profits or .orgs to be created (a task that's almost impossible in any case). But capping them is fundamental to the freedom that the internet must keep having as a greater end.