Oh yes, Philip's perspective is valid. Buy in services and you'll hopefully have a better book. But the idea that you literally cannot publish without a $1000 budget is absurd.
In my personal experience, publishing through two small publishers and also self-publishing, there's not a lot of difference. Neither has sold many more than 100 copies of any title.
In terms of official stats, a report out a few days ago by the ALCS said that hybrid publishers (who ask the author to pay towards the cost) typically sell 67 copies, including the ones the author bought!
Obviously, if you end up with a big publisher who can back you with a big marketing campaign and get your book into supermarkets, you can expect to do better. It varies enormously.
Here's a piece I wrote on Small Publishers vs Self Publishing. https://medium.com/writers-blokke/authors-do-you-prefer-small-publishers-or-self-publishing-ffb45367bfea