Of course, any attempt to obtain serious amounts of power from space will
utterly dwarf today's space programs, so assuming that its costs will be
similar is ridiculous.

Absolutely. But, even if we are talking about Manhattan Project sized
efforts (which is really the crux of space cornucopia proposals) I'm
can't find any data supporting the preeminence of solar power.

Oh, and don't forget the costs of the storage systems you need for wind
and Earth-based solar, and the fact that tidal and geothermal are
cost-effective in only a few particularly favorable places, and the limits
imposed on fission by uranium supply.

Isn't the problem of supply obviated by using breeder reactors? And
what about the kilotons of U238 in storage?