Tor Browser is both free, and a hell of a lot more secure.
Tor browser is not free. The cost is externalized. It is run by people who see value in the community.
If you use mullvad, or safing spn, your paying directly to support the network without externalized costs. Both are good options.
If you have the means, and ability, I highly recommend donating to run a Tor node or running one yourself.