Custom/low-volume manufacturing done by shops that specialize in lenses for the scientific market is expensive. I have one lens that was $40K Forty Years ago. The Pentax UAT 85/4.5 was $1400 almost Fifty years ago. Look them up on Ebay now- expensive. I toyed with the idea of sending mine to Chris to have converted to M-Mount. Would be great on the M Monochrom.