Not rare, but far less common than Morgans. Peace Dollars did not have the “wet mint bag” method of storage, so there are far fewer toned Peace Dollars.
Sold a couple of worn bust halves a while ago for ~$30 ea. Sounds low but they were on my page with no buyers for almost a month I think. There aren't any coins I *terribly* regret selling, but if I could buy back the busts I sold then I would do it, just to have them in the pre-1840 silver bucket. I honestly have a bad habit of keeping the nicest coins to myself. That's probably why my regret sell list isn't that big.
sold 2 ms-67 fh1916 slq for 90.00 each to bowers and ruddy galleries back in 1980 then sold 4-1921 peace dollars, all grading ms-63 to 65 for 250-400 each at a coin show, wish i had them back at todays prices..but the peace dollars i had bought for 90.00 each, and the 2 slq i got for 2.00 each, both were horribly toned (almost black) used tarn-x, then a hot water bath afterwords, let dry, voila..gem bu high grade, and they passed the rigid standards of bowers & ruddy galleries buyers inspection and i got a cheque in 5 days..for 180.00....do not want to get into all the silver i sold to buy my first house (at 12.50 on the dollar, lol) bars and over 400 silver dollars f-au....both morgan & peace....(sigh)