Original sentence: These companies are often able to offer their services with little or no upfront cost to the author, however they are still considered vanity presses by many writers advocates
Edited sentence: During the first years of the 21st century the mainstream printing business went into a slump and the gross oversupply of digital printing machines (like big Xerography machines with add-on units to bind books) forced traditional printers as well as the new print on demand companies to seek new sources of revenue.In some cases, the copies are not even bound.Some have turned to scamming authors in order to keep their machines busy and to help pay for them