Are unit tests free when TDD-ing?

Interesting post from Cory Foy, who quotes William Petri. More ammo for people who are trying to convince their colleagues/bosses/etc. that you don't waste, but on the contrary you gain time when you do TDD -- or TED (Test Enhanced Development) as I dubbed a variant of it: write some code, write unit tests for that code, then write more code, then more unit tests, etc.; note that the person writing the initial code can be different from the person writing the initial unit tests.