You get all of these (below) benefits, but you don't get the MAIN benefits, which include forcing yourself to formally describe to yourself the result your code needs to produce before you start, which produces better design and also writing all those mocks forces you to understand your dependencies really well. A developer who uses TDD consistently is just better and hence will be lots faster, even though she might be writing several times more code than someone who does not.

In addition, using TDD is often faster in its own right, because it allows you to work around things like a broken back end (in cases where you're a front end dev and the setup requires you to have a live backend connection) and you don't have to manually do all the clicks to navigate to where your code executes.