The most obvious thing is bio-tech, protein folding, drug discovery, etc. As in, things that have an actual positive effect on humanity (not just dollars).
I don't really get people who are dismissive about this aspect of AI- my original question wasn't about cost-efficiency of developing these things, but just that the technology itself is creating things that wouldn't have been possible before. It seems hard to refute.
Whether or not it's worth the cost is a different debate entirely- about how tech trees are developed and what the second order effects of technology are. There are so many examples- the computer itself, nuclear power, etc. I think AI is probably on the same order as these.