There's a question of cost though. Each repair job costs about $1 billion and has a ~1% chance of killing the crew. (When Hubble was designed, it was thought that the Shuttle would be cheaper and safer than it was.)
If we could build an launch a Hubble for $1 billion, then it's obviously cheaper to send up a new one than repair it each time. If it lasts for 10 years, then if the unit cost to launch were under $3 billion then it would still be cheaper to launch a new one than fix one in-place.
So how much did Hubble cost? Wikipedia says $2.5 billion to construct. http://www.nasa.gov/pdf/499224main_JWST-ICRP_Report-FINAL.pd... says "Again, to put this in context, HST, which was a much less complex mission [than Webb], had a total cost-to-launch of approximately $5 billion in current dollars. Hubble’s LCC was approximately double this because of servicing costs over 20 years." (Those are 2010 dollars.)
Hubble also had huge cost overruns. The KH-11 has an estimated unit cost, including launch, of US$2.26 to 3.16 billion in 2015 dollars, says http://en.wikipedia.org/wiki/KH-11_Kennan#Cost . We've built several of those, which I assume helps reduce the per-unit costs.
If we could get the Hubble-like unit cost, including launch, down to $2.5 million, and with a 10 year life time, then we could launch 4 for what we've spent on Hubble, and lower risk through redundancy. "No serviceability" = "cheaper design" = "can launch more" = "lower risk". Again, this is based on the experience since the 1970s that manned missions are expensive and risky.
Regarding just because - your original question was "How would you have gotten even one HST sized telescope into orbit without a manned mission?" That's all I'm addressing.
Yeah - I take it back - I spoke too quickly. You can certainly launch large satellites with rockets. I was too focused on Hubble specifically.
That said, I remain deeply skeptical of the idea of being able to do so cost effectively or in a way that allowed for iteration and development of the systems. That's a lot of eggs in one basket to make 4 duplicates - they'd all fail in the same ways (which Hubble did early and often) and they'd be space junk in a heartbeat. You'd also want different cameras, which would have different requirements, etc. Once the contractors got a hold of that, they'd wind up 4 separate projects costing a fortune, and you'd be right back where you started, except without the budget. Keep in mind how long it took to build the HST. A servicing mission turned around in about 3 years.
It wouldn't be duplicates. A better plan would reuse the same chassis, and have a staggered production. There have, after all, been 16 KH-11 satellites over 30+ years; they surely didn't all use the same technology.
Part of the reason for the expense of HST comes from the delay after Challenger. Hitching it to the success of the Shuttle helped make it more expensive.
You are right though that it plays to the sunken cost fallacy. Hubble happened because the initial budget was low. Then it ballooned. Congress would likely not have budgeted $10 billion if they knew that was going to be the final cost of Hubble. It's even less likely they would have funded four space telescopes for that price.
There's a question of cost though. Each repair job costs about $1 billion and has a ~1% chance of killing the crew. (When Hubble was designed, it was thought that the Shuttle would be cheaper and safer than it was.)
If we could build an launch a Hubble for $1 billion, then it's obviously cheaper to send up a new one than repair it each time. If it lasts for 10 years, then if the unit cost to launch were under $3 billion then it would still be cheaper to launch a new one than fix one in-place.
So how much did Hubble cost? Wikipedia says $2.5 billion to construct. http://www.nasa.gov/pdf/499224main_JWST-ICRP_Report-FINAL.pd... says "Again, to put this in context, HST, which was a much less complex mission [than Webb], had a total cost-to-launch of approximately $5 billion in current dollars. Hubble’s LCC was approximately double this because of servicing costs over 20 years." (Those are 2010 dollars.)
Hubble also had huge cost overruns. The KH-11 has an estimated unit cost, including launch, of US$2.26 to 3.16 billion in 2015 dollars, says http://en.wikipedia.org/wiki/KH-11_Kennan#Cost . We've built several of those, which I assume helps reduce the per-unit costs.
If we could get the Hubble-like unit cost, including launch, down to $2.5 million, and with a 10 year life time, then we could launch 4 for what we've spent on Hubble, and lower risk through redundancy. "No serviceability" = "cheaper design" = "can launch more" = "lower risk". Again, this is based on the experience since the 1970s that manned missions are expensive and risky.
Regarding just because - your original question was "How would you have gotten even one HST sized telescope into orbit without a manned mission?" That's all I'm addressing.