Short answer, because you didn't ask for a biography; $100
Longer version:
Wow...
Either some of you guys are some real high rollers with more cash than I've ever had or I'm just really cheap.lol.
Y'all talkin' about $600, $750, $1,000 or $1,200. A few even went over $2,000! For just a single knife? If you guys have too much cash and just need to unload a little feel free to pm me for an adress! Lol. I wouldn't mind at all to help.
I've been a knife nut since I was a small child. Edc-er since I was 9 and never even heard the term until years later.
Really, the only time I've ever broke the $300 limit was years ago. I was a teenager, the Cold Steel catalog came in. They were coming out with the Warrior Series and I HAD TO HAVE an O-Katana. I worked extra hours at my entry level job and saved money as best I could for over 2 months and took a special road trip with a friend to Smokey Mountain Knife Works to claim my treasure. Nearly $400 spent on the one toy IIRC.
Turns out I wasn't a legendary Samurai or even a Ninja Warrior. Who knew! It may have been news to me at the time. Lol.
One of the most disappointing purchases of my life. I still have the sword because even though I have no purpose for it what-so-ever I doubt I could sell it for much of anything. I refuse to throw it away because... I don't know why. So my $400 sword is sitting in the corner of a storage shed.
Only other two knives I own that went over $200 are both in use and are great knives but not as impressive or amazingly awesome as they were on my imagination. Or the advertising and reviews. Not near as disappointing as my super Samurai weapon, but they certainly didn't justify the hype and build up. Yes, I do use them.
Anymore I mostly buy sub-$100. Often I buy used from the flea market. That's where I got my Leatherman Charge Ti for $30 IIRC. Got my Buck 112 for $8. Etc. Etc.
Also shop the big auction site alot. Just got an Alox Pocket Pal from Victorinox in great condition for about $11 delivered and am very happy with it.
Anything over $200 and you're in firearm territory. I look at a knife that's $400 and think "I could buy another Glock for that!". A little more and I could buy a nice Ruger magnum. I'm a revolver guy.
At the $2,000+ range a few of you guys mentioned I can't help but think "I could buy a Jeep for that! With money left over for a few groceries and a night out with my wife!".
I don't see the value.
Diminishing returns is a real thing in my humble opinion. It'll have to be a very sweet knife on a day I'm packing cash and feeling extra spendy to ever break $100 on a knife again. I'd rather hunt the bargains. It's more fun and more rewarding for me.
To each his own. Enjoy your blades guys. A great day to all of you.
Carry on.