Here's what Wikipedia says on their word count page:
"Novelist Jane Smiley suggests that length is an important quality of the novel.[3] However, novels can vary tremendously in length; Smiley lists novels as typically being between 100,000 and 175,000 words,[4] while National Novel Writing Month requires its novels to be at least 50,000 words. There are no firm rules: for example, the boundary between a novella and a novel is arbitrary and a literary work may be difficult to categorise.[5] But while the length of a novel is to a large extent up to its writer,[6] lengths may also vary by subgenre; many chapter books for children start at a length of about 16,000 words,[7] and a typical mystery novel might be in the 60,000 to 80,000 word range while a thriller could be over 100,000 words.[8]"
That page is at
https://en.wikipedia.org/wiki/Word_count
I think if I paid $10 for a 29,000 word novel I'd be unhappy but I have to agree that it doesn't seem to be a scam so much as too-slick marketing.
Considered among the many sneaky things publishers do I can't see this as a major one.
Barry