To date the most expensive single shot I've bought is a Shiloh, and it is a wonderful thing and a heck of a value. I've nearly pulled the trigger on a Dakota M10 a couple of times, but one of the really fine handmade singles is very attractive, too. Such a gun would probably be a bucket list deal for me. I enjoyed chatting with Ralf Martini at DSC, who was amused by my Shiloh t-shirt.
AFreeman, I've wanted a original Fahrquharsen to add to the collection, but good ones are up there a ways and the few I have seen I just could not swing at the time. I had not heard they have internal issues, so that's good to know. I did enjoy working with a Field's Patent falling block a few years ago, even though it was heavily worn, and I wish I'd been smart enough to keep it.
If I do jump on a Hagn, or Soroka, I'd probably skip the engraving, and just focus on really good wood. I'd shoot it, too...