Because Amazon moved from selling products (and setting 100% of prices) to inviting competition from new and USED products, including letting those compete against its own listings - we are going to bust them for anti-competitive behavior?
There are entire catagories of product where you can save a ton with almost no loss of function by buying used.
Amazon has lowered per unit cost on everything from ebooks to other products because they have data showing increases in demand will beat out loss of net margin. They've sued publishers to try and drive down prices or be able to set lower prices than publishers want. They will generally accept much lower margins than a corner retail store.
They offer all you can eat books (KindleUnlimited) which dramatically LOWERS the per unit cost of books for heavy readers.
Same thing with Prime, they are driving a far far lower per unit cost with movies and music.
The worry should be that Amazon has been an absolutely ruthless competitor since day one. Good union jobs at UPS may be threatened if Amazon thinks it can do the job cheaper with dirty renta-vans and contractors. Any high margin business out there should be a little worried - for example, pharmacists making $175K+/year should wonder what happens if Amazon does 2 hr delivery of Rx with computerized interaction screening. And this is all clearly anti-competitive?
They have a whole platform around de-skilling and automation. Their warehouse workers are told, literally second by second where to go and what to do - fully sequenced and monitored including discipline. This doesn't strike me as a process that will increase prices.
They also do seem to screw - not their customer, but merchant partners from time to time. Customer says product was defective to avoid a return shipment fee. This is actually pretty common. The warehouse DOES NOT do much screening to see if this is true. The customer is not asked for specific details. I'm sure some customer accounts are cancelled over abuse related to this but it seems likely to be low given the number of folks doing this.