A team of Federal Trade Commission investigators has begun interviewing small businesses that sell products on Amazon.com Inc. to determine whether the e-commerce giant is using its market power to hurt competition… The interviews indicate the agency is in the early stages of a sweeping probe to learn how Amazon works, spot practices that break the law and identify markets dominated by the company. The length of the interviews and the manpower devoted to examining Amazon point to a serious inquiry rather than investigators merely responding to complaints and going through the motions, antitrust experts say.
https://www.bloomberg.com/news/articles/2019-09-11/amazon-antitrust-probe-ftc-investigators-interview-merchants
Some of the merchants quoted in the article share how the FTC was particularly interested in how Amazon's advertising services pressured them to raise prices.
Put me down as unimpressed, at least with regard to the US market. I've been seeing articles like this on a regular basis for at least a decade. There are lots of antitrust investigations of Amazon but they never lead anywhere because its almost impossible for a general retailer to corner the market in the classic antitrust sense. Anybody can set up an online store, and many have, including Walmart, Target, Ebay, etc. Amazon just happens to attract customers much better than they do.
The key question for a judge will usually be how does a monopoly corner the market so it can artificially raise prices for consumers. For a long time now, academics and lots of Amazon's competitors have been throwing theories against the wall to see what sticks. So far, nothing has. That's mainly because Amazon is relentlessly driving prices down for consumers, not up.
The most recent antitrust theory I've seen involves house brands. Most retailers have had them for a long time, including Amazon. The theory seems to be that Amazon is giving its brands preferential ad placement on product pages, and it's using lower prices on house brands to kill the sales of name brand products sold by manufacturers and middlemen.
Keep in mind that Amazon generally has the right to exclude whatever products it wants as long as it doesn't discriminate using a handful of suspect criteria like race or sex to decide who it will do business with.
The OP mentioned a concern about Amazon raising prices, but the Bloomberg article puts it differently, and it matters. The article says, "Amazon, which faces little competition online, has been raising fees and selling advertising—forcing merchants to raise prices."
My response is, so what? Amazon can exclude products entirely, and it can also charge middlemen and manufacturers whatever price it wants for the privilege of listing their products in the Everything Store. Similarly, Amazon can charge whatever price it wants for the privilege of running ads on the Everything Store. And it can give its own products ads that aren't available to anyone else. That's just business.
Please note that my lack or enthusiasm for these antitrust claims against Amazon is based on US law. In other countries, the laws can be quite different, and Amazon may run into serious problems in Europe, for example. It already has with regard to books, where many European countries have set up special pricing rules to protect small bookstores.