If you're an academic, or want to be taken seriously by other academics (eg you're a self-educated expert) you want to be published in a journal because citatio

If you're an academic, or want to be taken seriously by other academics (eg you're a self-educated expert) you want to be published in a journal because citations that link back to your blog will get you tagged as a crank - perhaps fairly, perhaps not. If your target audience is open-minded you can compromise by publishing on Arxiv.org or a similar site, but a lot of people will reflexively dismiss your work because it hasn't been through the peer review process. The idea of peer review is a very sensible one. But (much like search engines) the process can be gamed by unethical actors; and where scarcity (of academic prestige) is enforced, rent-seekers invariably follow. Peer-reviewed journals charge a lot of money to submittants, but they generally don't pay the reviewers any of that. The money mostly goes into 'editing' - which is a little bit of curation and mostly proofreading - and administrative costs.