> to not nauseate the human body, they need to be fairly large

I completely agree with your reasons why it hasn't been explored further (sadly budget issues killed even a small experimental module for the ISS[1]). Just how large is somewhat disputed though[2, pages 20-22]. By these estimates, ~10 Starship launches (ballpark $100M-500M launch price tag) could loft a dumbbell-shaped rotating station into LEO.

1: https://en.wikipedia.org/wiki/Centrifuge_Accommodations_Modu...

2: https://space.nss.org/wp-content/uploads/Space-Settlement-Po...