Is BDD with RSpec cheaper?

This might be a loaded question on this forum, but here goes:
Just had a discussion with a prospective employer, a Ruby On Rails shop. His reaction to BDD development on every project was skeptical, saying something like: "It depends on the project". "Some jobs are so short that the extra time invested in developing tests doesn't justify the cost".
He was insistent that writing tests costs more. After all, you write twice: first the tests, then the code (or the other way 'round).
My question is: From hard, practical, cold real world experience, is that so? Is BDD development more expensive? Let me qualify that. One could answer, "no, since the tests save you pain and heartache down the line". The question is whether BDD coding with RSpec is more expensive in the implementation phase and how much truth there is in the statement that BDD isn't for every project, like quick knock ups for example?