[jasonmorton]

There are some high-quality open access journals (e.g. https://www.emis.de/journals/SIGMA/) that don't charge authors. They use arxiv overlay. It is entirely possible.

[Nemo_bis]

A few hundreds more are listed here: <https://doaj.org/search?source=%7B%22query%22%3A%7B%22filter...

[dmitriz]

In fact, as are all journals from Free Journal Network https://freejournals.org/, of which SIGMA is a member.