[mannerheim]

Even accepting this premise, there's no reason to pick the most expensive option for manned spaceflight.

The ISS cost $100 billion to launch and assemble (and $3 billion to maintain). Tiangong about $8 billion, reportedly. Mir, some $4-5 billion.

The total project cost of Dragonfly mission to Titan (to be launched in 2027 and landing 2034) is projected to be $1 billion. Even the JWST, which had massive cost overruns, still only cost $10 billion. If the NASA built a Tiangong instead of an ISS, who knows what they could have done with the remaining $90 billion. Maybe for a few billion, they could have sent a probe to Europa to search for life under the ice.