Anyone done this?
A key part of gaining a PhD is getting your papers published. Initially it usually requires being a co-author with an established academic. Towards the end of your programme you might be lucky to get 2-3 papers published after a great deal of revising and editing. And of course, all that is based on leading edge research, i.e. work that builds upon prior knowledge.
Many journals that charge to publish your papers are basically scams and viewed with derision by academics and experienced researchers.
Failing that you can always just submit to Arxiv or another preprint server. If you want to disseminate and get the credit, that's usually good enough.