As sheldon brown says here, http://sheldonbrown.com/vrbn-a-f.html#bianchi "Top-end Bianchi models from the early 60's through early 70's should be worth close to $2000."

Obviously, thats an estimated value, some go for higher, but again, top-end 60's/70's. Late 80's was a tough time for a lot of big name bike brands, and things cheapened up, so that stuff simply isnt sought after like the earlier years.

All cleaned up, and i'm going to assume completely clean of any rust (which i highly doubt you can ever get it to mint), but to give you a top value... Maybe 800-900, and thats IF you found the original stem and seatpost/seat/frame shifters.

I personally wouldnt pay over 500 if that stuff isnt on the bike.