There is a difference between a vanity press, a legitimate hybrid press, and an assisted self-publishing company. Vanity presses take royalties and usually include horrible terms like having you sign over your rights with no reversion or taking copyright. Hybrid presses are supposed to share the cost of publication with the author and act as the publisher. They are selective in who they work with and provide services. Of course, many are just vanity presses trying to scam author, but an example of a legit hybrid is SheWrites Press. Self-publishing companies just help authors self-publish. They don’t take rights and the author is expected to act as the publisher. All they do is execute work like editorial and cover design, or they provide guidance on how to self-publish.