Hmmmm..... buuuuut I have read somewhere recently that Amazon has about 5% of all published books. I have a hard time finding more obscure things on there, especially non-fiction. Does Amazon have an emphasis (on fiction) or how do they pick?
If it is true, then it would seem like being listed on Amazon is a fun goal -- any of your friends can see you on there! -- but won't make a huge difference to your sales unless you are self-pubbed or something. Yes? No?
Having worked for a small press publisher and setting up the account with Amazon, I can tell you basically how it works.
Amazon doesn't go to the publisher, the publisher goes to Amazon. When I established the account with them, I went to their website, followed the directions (this was many years ago, so it's likely to have changed but it was clearly marked--Had to be--I'm a computer dunce) and sent in an application for contract with them. They responded with a contract which stated the terms of payment, shipping and discount (all of which sounded outrageous to me, but the boss went for it with a big smile on his face). Then it was my job to upload all the information for each of the books we offered onto their website.
As long as you ship books when they request them in a timely fashion and no one accuses you of breaking any laws, they just let you do pretty much maintain the pages yourself.
When I had my book small-press pub'd, my publisher opted NOT to sell on Amazon or any of the other sites because of the demanded discount and terms of shipping because it was cost-prohibitive to them. But, then again, they went out of business about 3 months after my title came out, so my numbers are non-existent anyway. LOL!
Knowing what I know of Amazon's standard contract, though, I wouldn't sell anything self-pubbed there. I agree with my publisher--it just isn't cost effective enough to bother with. The small press publisher I worked for before sold off his website, Amazon and via a monthly newsletter (outside of previous customers) and out of his annual $2 million business, at least at the turn of the century (still weird to say that), I can attest that Amazon sales only resulted in 36-50 books a MONTH. Diddle, compared to what we sold elsewhere.