Too many authors tell us that they publish via a subsidy/vanity house because they "can't be bothered" with details like ordering their own ISBNs. The subsidy houses go by a bunch of misleading aliases, such as "POD publisher", "self publishing company", "author services company" or sometimes just "POD. But if you pay them to publish the book under their imprint an using their ISBN, then they are a subsidy. If they pay your a "royalty" instead of just charging you for printing/fufilling the books then they are a subsidy.

Two other things subsidy authors  apparently can't be bothered with:

1. Making money, or at least breaking even.

2. Getting wide readership.

Subsidy presses make it easy to publish a book but hard to sell it.  The  pricing on even the cheapest subsidy costs twice what it would cost to print and fulfill via a POD printer such as LSI. And meaningful prepublishing reviews with the big five prepub reviewers are just not availalbe to subsidy published books. With narrow margins you can't sell via bookstores or Amazon Advantage. A distributor is out of the question.

Most subsidy books fail in the marketplace. Bluntly most are not worth publishing in the first place. The subsidy house makes money from authors and sales to those authors. But what if you succeed? What if your book takes off and you start racking up sales? Now you are in even worse shape. To get decent margins you need to take over the publishing of your book.  You may need to print offset.  But once you have published subsidy you are more or less stuck. The favorable publicity attaches to the ISBN, and the ISBN is the property of the subsidy publisher. The same goes for the interior layout, the cover art, and so on.

The more glowing the promises the worse the deal.  Bottom line, don't publish subsidy.

The best of the worst are these three, in order of preference.

Booklocker.com

Lulu.com

Infinity.com