I'd say about $100 and I'll have a prepaid shipping box off in the mail to you tomorrow!
Seriously, I am waiting on delivery of one that I paid Handejector $750 for shipped. He had it in the classifieds for $800 with an extra pair of banana stocks that were never factory issue on anything I own so I bought without the bananas. I do not actually know what anyone else would pay for one. There are a few on Gunbroker that have been sitting there for one to three months at $800 to $1,000.
As you must already know, the handgun market in general has shifted away from long barrels and shorter barrels are more likely to bring premium prices or sell faster. If I had to limit myself to just a few K22s an 8 3/8" full lug would not be one of them.
Best regards;
Gil