Hardly. The big cost of any manned space mission is launch, and SpaceX already has that licked. Even if they were to use the Falcon Heavy as the basis for a Mars mission they could easily do a several landing mission for less than $20 billion, this is well within the costs that various studies have shown is possible for a Mars mission. And that's potentially within their long-term accumulated profit margin over a period of several years. If they manage to bring costs down further, which is something they've already demonstrated competency at, then the idea of a $5 billion or cheaper Mars mission is well within the realm of possibility.
