Here’s an example where Amazon strait up increases prices.

There’s a great deal of self published fiction posted online for free. Amazon is happy for people to sell bundle that into a book and sell that.

Kindle Unlimited specifically requires authors to remove earlier copies of their own works to become part of kindle unlimited. Thus increasing the minimum price for everyone above what it would otherwise be.

Some authors make the transition and win, but many destroy their audience and thus current and future revenue sources like donations and patron subscribers. It’s a tempting infusion of cash, but the long term consequences can be devastating making the whole thing really predatory.