Comment by __tg__

Not sure about the Starship numbers but if its is $2m per Hubble mass, then launching 200 hubbles would be $800m, not $43m. This however is not about sending bricks into orbit. The ELT mirrors are segmented and need precise alignment with each other to micron precision. Deploying a segmented mirror in orbit has still not been done (the James Webb Telescope launches in 2021); the engineering involved adds orders of magnitudes of complexity over a single-piece primary mirror such as Hubble has. Add to this maintenance costs: a mirror the size of ELT in orbit needs a huge maintenance program behind it to work at all. The lifetime cost for such a mirror would be in tens of billions, if not hundreds. This is why such large telescopes keep getting built on Earth.