Misko,
Welcome. My finest user is my Ed Fowler bowie. It's in his book, second pic page, top knife. Is it expensive? I don't know....if it lasts only a copuple years in good working condition, it was expensive. If it holds up real well for the next 20 years, it was cheap. Before I started using it, I guess it was worth $1000 to $1200. Once I decided to turn it into a user, on the good advice of Kodiak PA, I tapered the blade edge a little towards the tip, and put a razor sharp polished edge on it. Decreased the value to others and increased the value to me. It's the perfect all around fixed blade.
I wasn't going to do this, but I have to. Sorry, man! My most expansive knife, which I no longer have but wish I did was an inflatable sword which I got when I was 3 or 4. It was factory, not custom. It was not differentially hardened, but you could adjust the overall hardness for the job at hand by blowing more or less air into it. For chopping, say on my brothers head, I would inflate it to about 6 Rc. For slicing, as in an actual swordfight, I would need to blow harder and inflate it to about 8 Rc. I believe that this type blade was the precursor to the differentially heat treated blades you see today.
I like bladeforums and consider the fellow forumites to be my friends. Some more than others, of course. Kodiak PA near the top. You'll find these guys like to have a little fun when the opportunity presents itself. So do I. It's not serious and these folks know a lot about knives. So, welcome and join in!
Pete