Re: "... could cripple ongoing research efforts..."
If you're working purely on money, it's a very interesting question if Apollo was actually worth it. Sure we developed a lot of tech - but some of that tech would have come anyway from missiles and other military work. From memory Apollo cost around $24 billion 1960s dollars! That's pre-70s inflation money. You have to look at the opportunity cost of all that moolah.
After all, spy, GPS, weather, mapping, and communications satellites were going to happen anyway. Which would have got us some of the tech, and are the parts of the space program that have 'paid their way'. The manned space program hasn't given us a direct pay-back at all. Obviously medical sensors and such are great, but then all those billions could have been invested in medical research instead - and we'd have got the same thing.
Again what has un-manned deep-space research got us? The earth sciences satellites and the solar-activiity stuff is important, but all the planetary fly-bys are just for fun and the advancement of science. I suppose we may have got better at geology because of it, and that does have practical applications. Obviously basic research is a public good, and you never know what you'll get.
As you say, the shuttle was a dead-end. Although I'm not sure if that was obvious at the time - and I wonder if we were to have fewer military compromises we could now do a better job, with modern materials science. But I suspect not. I think Musk has some of the answer, with re-useable rockets and capsules. I don't know if it's worth re-using the 2nd stage or not. And there's hope for the SABRE engine too.
But the ISS has actually achieved some practical benefits already. It's paid back some of its investment. Admittedly it's boring old political / diplomatic. But it was part of binding Russia into a post Cold War world (even though that might now be falling apart). Also it was explicitly about keeping the old Soviet ICBM infrastructure working, when the Russian economy was collapsing. That's no small thing, given that in that time period North Korea, Pakistan Iraq and Iran have all been doing heavy nuclear weapons and missile research. As well as trading both technologies amongst themselves and to others. Without the ISS, North Korea might have a working IRBM (even ICBM) to go with its barely working nukes.
I was listening to a Radio 4 program about the disappointment about the research conducted on the ISS. I believe there's more going on now, as the thing's built. A lot of the early stages were spent putting it together. These damned Ikea flat-pack space stations take forever!
But a lot of that stuff is still going to be basic research that has no immediate/obvious pay-off. There's the alpha dark matter detector, and aren't they about to try one of these electric plasma engines on ISS too?
So yes, lots of ISS stuff is basically practical research into manned spaceflight. And if you think that's pointless, I guess the ISS is a waste of cash. Although the ISS has given the US the impetus to fund SpaceX, which is going to make satellites much cheaper. And that's a definite plus point in its favour.
I'm no chemist, but I always understood that there was hope of super new medicines / useful chemicals that could only be made in micro-gravity. I don't know if that's still believed to be the case. But obviously that's going to require decent numbers of humans living in orbit. And no way is that going to happen without government pork getting laid out in vast amounts first, to learn the technology. Also asteroid mining ought to be perfectly feasible - and give us extra resources that don't kill the environment. Once you get a space economy going, it's going to be somewhat self-sustaining, as power would be incredibly cheap, once you could make solar panels in space.
Also there's the topic of space defences. Chelyabinsk nearly took a hit last year. If the Tunguska impactor hit London or New York, you'd be talking hundreds of billions of damage to the global economy. Of course there's only a few targets that would do damage worth the investment to build counter-measures, and we don't know how frequent actually dangerous impacts are. Plus there's much ocean to act as a decoy target. But the knowledge to do this is going to be applicable to moving asteroids around, so there's a huge potential economic gain. And a Tunguska level hit in a major city could have killed several million people. Money would likely be forthcoming after an event like that. It would be so nice if we could manage it beforehand...
So in conclusion, apologies for the mega-post, I'd say the ISS may almost have been worth it for the diplomatic-political advantages alone. It's helped to give us SpaceX, and is doing basic research into whether we can have space-based industries. Which will hopefully start to pay off this century. If it's possible, and actually worth doing.
It's also done some basic research, and is now doing more. But that alone is almost certainly not worth the money. Anything to add? Disagree with?