Not to beat a dead horse, but I understand both sides of the "cheap" vs. "high-end" argument. You can take a cheap knife and a bells-and-whistles knife, and use each 10 times, and chances are you would never notice any meaningfull difference, whereas when it comes to firearms, you'd likely know the first time you went to the range. But stretch that 10 out to a 100, carry it every day, put it through the wringer, and most of all, stake your life on its performance, and that's when you'd trade up, as best as your financial situation will allow.
Back when I had more than a snowball's chance of getting into a life-and-death fight, knife or otherwise, I carried a lot of gear like Geoff Timm alludes to. If you're going to be issued a bayonet anyway, a large knife is not on your packing list. As some have already observed, a bayonet at the end of long arm is a formidable weapon, and believe it or not, some of us were/are actually trained in its use. And of course, you can use it as a big knife, fighting or otherwise. To this end, the current M9 bayonet is a big improvement.
I never got to use a bayonet, but I have survived in the field for weeks at a time. When it comes to the myriad field tasks that others have so rightfully observed, I found the good ol' Buck folding hunter, augmented with a Swiss Army knife, more than agreeable companions.
So why own a "fighting knife"? I don't know, why own three custom 1911s? Just in case is probably the answer, coupled for appreciation of quality. I personally have subscribed to both sides of the fence on this isuue.
I just recently went on a trip to Hawaii. I wanted to bring something for defense, but I was certainly not crazy enough to bring a gun. I bought one of those "Ranger" knives, 5" blade, subdued, with the paracord handle, for 5.99. I carried it in the open, attached to one of those backpacks that tourists can't live without nowadays, and didn't raise an eyebrow. I'm sure it would have been more than adequate for the one time I would have used it, if necessary. But I wouldn't care if it was lost, stolen, confiscated, or ditched.
But "back in the day", I bought a Randall #14. If I was recalled to active duty for a special 3-day commando mission to snatch Osama because of my special skills (cigar smokin' and beer drinkin'), I'm sure I'd bring the Randall with me.
However, for a longer-term expedition, public or private, I think my Cold Steel Trailmaster would get the nod. Clearly it has utility for fighting, and is a little more sturdy for such chores as brush clearing, opening crates, etc. I would augment this with a SOG Paratool, Leatherman, or the like (those pliers are indispensible for removing cactus needles, as folks around here can attest).
As an all-round back up, I would carry my Benchmade folder.
Hopefully, my trusty ol' Buck knife won't take offense.
Blade is 9+alittle and 2in wide Carry IWB every were when I was trucking. They been sliceing and diceing with these in Spain for over 100 years In old times some were 39 in open and you thought you Cuda Max was large. 
