As someone who's done freelancing previously for years and also has run an agency previously for years, it really depends. I've certainly seen freelancers at double or triple these rates. If you already have clients, are well known, or you're good at selling the value of your time, you can ask for much higher. If you're just getting started or you're going through an agency, these rates seem pretty competitive. Also macro economic factors will change the equation and what you can ask for.

For those just getting started, my piece of advice is to be OK taking a lower rate initially, and just keep pushing it higher until you find resistance. If you're good at what you do, you will quickly find that you will get referrals (make sure to ask!) and can charge a ton more. It's a lot easier as a freelancer/contractor than a salaried employee since the market is much more liquid (you spend less time at one gig) and therefore you can test the waters with a higher rate much more often.

Regardless, what these companies list as what they will pay hourly isn't necessarily what you have to ask for. If you think about it from a negotiation perspective (and you have the ability to sell yourself), these are simply just the lower bound of what you can ask for.