The way the anti-trust laws are written, there are limited avenues to keep companies from raising prices as long as they don't collude doing so, instead, they simply incorporate the expected actions of their rivals in their own decisions and the result is an equilibrium with above market prices.
It's illegal to monopolize, but not be a monopoly, that is, if you use predatory pricing to drive competitors out of the market or other mans of gaining market power you can be prosecuted, but if like Amazon, you're simply smarter and more efficient, that's perfectly legal, as it should be. Amazon has driven down prices across the economy and provided needed services to those in more rural area, who are disabled, and yes, the poor living in retail "deserts."
Apple is not an issue, they face plenty of competition in their markets, they stay ahead through innovation and marketing, but also have driven technological advancement. But they don't control the markets for phones or personal computers - they charge a premium for the perception of better quality and a well integrated "Apple World" which provides perceived benefits to their customers.
The problem comes when MIcrosoft, Google and Facebook grow, not due to their technical prowess, which certainly was true for the first two for an extended period, but by buying out potential competitors - that's where Antitrust enforcement has become more aggressive, stopping mergers that hurt competition. However, Microsoft and Google provided tremendous value, imagine the world without "Office" or the ability to "Google" anything (and Google Scholar is basically a charity, I don't see how they make money off it but it makes academic and legal research available to anyone). Keeping them from buying out potential competitors would change the focus of start-ups from chasing buyouts to chasing market share and becoming more efficient (and more dangerous competitors). But network industries aren't the big problem in the economy, the real cost of information services continues to drop - it's the increase in demand that keeps prices up (streaming 720 to 1080 to 4K video for example).
The root of the problem has been Michael Porter, whose books have taught MBAs for decades how to legally pursue market power by focusing only on markets where a company can be the 1st or 2nd largest competitor - the result is companies leave markets where they're 3rd or 4th largest by selling assets or merging, instead of trying to compete on price, reducing competition. This overall shift in corporate strategy has increased market concentration in most conventional industries. This will be tempered when consumers search for lower cost alternatives and stop buying "branded" goods.