Looking at the English rules for the second edition the wording is, "...has to pay $4 + normal cost for each hex built this round.". This seems to indicate that it is only paid if building and is per hex not just for the entire build.
Sorry to revive this older thread, but I was wondering if anybody ever got a definitive answer to this question. I think the rules could be read either way. The additional $4 per hex just seems way too brutal to me, but I agree that it would seem to only apply if you decide to build. How are folks playing this?