Self-publishing is not without its problems.

Peer review, while not perfect, guarantees that the text has been reviewed by quality researchers. Journals have an interest in filtering bad publications, if only to keep their reputation.

In contrast, a self-published paper has no guarantee of quality, simply because everyone can do it. An author's reputation is often a proxy to assess a publication's quality, but this is clearly bad for new researchers.

I think there are good alternatives - my last publication costed around $300, which were used to pay for the conference where I presented it.