First of all, there are many free fonts but most of them contains a very narrow subset of characters. If you want a complete font with 3000+ Latin+Greek characters and variations like old-style numbers, small-caps, ligatures and so on, that's a massive work behind it. And also, as an individual, of-course it's expensive to pay hundreds of dollars on a complete font-family, but for a company making money on graphic design that's really not a problem.