I buy them used, there's no way I could buy them new or replace seals at that price. Most of the time used calipers aren't cheap, so it takes some looking to purchase them at a reasonable price. Left calipers from R/K 1100's or R12C's. R1150's used a Tokico caliper and I think mount spacing is different.
It's just milling off some material, search and you'll find my post or others on the subject.
If you send me a left caliper I can have yours done for $65.00 plus s&h. For simplicity's sake USA only.