Clem, nearly the only reason to get a "legendary" lens is to have braggin' rights. If you're willing to spend money for that, well, its your money ...
Thing is, many "legendary" lenses are no better than similar lenses that aren't legendary. There are a couple of exceptions. A class of lenses, soft focus types. They're not all functionally equivalent and if that's what you want you'll have to pay the price. The Goerz Hypergon. Again, there's no functional equivalent.
Coupla examples of legendary lenses for which there are substitutes, possibly superior:
Goerz Serie III Doppel Anastigmat, later sold as Dagor. Legendary as can be. Other makers sold equally good dagor types that can often be had for much less money than the equivalent Dagor.
Goerz Apo-Artar, a four elements in four groups process lens. Also legendary as can be. Thing is, uncoated ones aren't that wonderful because of flare. And Nikon (symmetrical type Apo-Nikkors) and Rodenstock (Apo-Ronars) made functionally equivalent, possibly slightly better, 4/4 dialyte type process lenses, all coated, that generally sell for less than the equivalent Apo-Artar.