The issue I have with Amazon is that for many folks, they ARE the marketplace to buy goods. Pushing their own products as the "best Cyber Monday deal" is when things get a bit suspect, at least for me. And honestly, what represents "Best"? Best for the consumer? Or, best for Amazon?
(My cynicism is probably due to working retail (Staples) and having managers push us to sell Staples-branded items due to higher margins for the store/company (and we sales were happy to comply due to the higher spiffs). While I truly enjoy on-line shopping since I no longer deal with sales people, I'm fully aware that the algorithm pushing that "BEST CHOICE" IS the new "sales person". And they know more about me than any sales person in a physical store would ever know...scary.)
I'd argue this will vary with dealerships. And, the pushiness would be more sales person, rather than the dealership.
For new cars, there are a couple reasons why a dealership may push a new car over a used car. The manufacturer may be providing volume incentives and the dealership needs to sale a certain number of models to meet that incentive. Or, a new vehicle has been sitting on the lot for too long and the dealership needs to move the vehicle (this is more true for used cars).
But, USED cars are a cash cow for dealerships. Either through trade-ins or auction purchases (based on the type of dealership), there's WAY more margin in a used vehicle than there is in a new car.
Unless it's a purely volume-driven dealership, dealerships will be perfectly happy to push a used car over a new car.
What I find more troubling is that the default sort order for browsing search results and categories etc is stuff like "Sort by: Featured", "Bestseller", interleaved with "Sponsored Results", bla, bla, bla. What I want to know is which button to click for "please make a goddamn effort to show me the stuff where it's in my best interest to see it, given the query I gave you, or given the category I browsed into, rather than in your best interest or in the interest of someone who paid for the privilege of my attention" -- A long time ago, I had some level of trust that online shops were able to deliver on that. But that's no longer true with Amazon.
They do own a website that accounts for something like 4% of retail sales.
https://www.bloomberg.com/news/articles/2019-06-13/emarketer...
That is utterly dominant. Market-shaping, even.
Also, is that 4% by number of items sold, or by total sale value as a fraction of total market transaction value?