That is an oddball Bianchi. The lug set, BB shell, and seat-stay top is the same ones used for late 70's to about '81 on the Italian Rekord models that were built with Zeta or Alle trubing. Same cable routing as well.

The second bottle cage bosses and the pump-peg would date it later (if they are original to the bike).

Is the BB confirmed English? I know the OP listed it as 68mm but did he confirm the threading?

Maybe Bianchi sent a bunch of outdated lugs and frame parts to Japan for the first models to be built there. Guess they sent tubes and drop-outs as well, as no other Japanese Bianchi's I've seen were SL with Campy drops?

As for price, I think $200-$300 would be fair. If Celeste you could double that.