For a lot of cases the answer is lobbying, e.g. in medical/healthcare there's practical 0 competition for a lot of products because of anti-competitive laws like really shitty intellectual property laws that let prices be controlled by few (collaborating) companies. Plus there's a lot of things that are technically illegal, but in practice laws only apply to the poors so they're not really illegal for corporations: https://en.wikipedia.org/wiki/Anti-competitive_practices#Types