The program might not have borne all the speculative fruits, but the one very major thing that has come out of it is the learning about the effects of living in micro-gravity on the human body. If ever we want to get humans out into the rest of the solar system, this knowledge is priceless. Oh, I know that NASA has this constant pressure to justify that learning in terms of stuff like "medical benefits" (and there surely are a bunch of those!) but really it's the foundational pure science that's critical here. I don't think there's any monetary value can be put on that.