Serious question... What could possibly make the folding knife on the first page worth $2,500? Is it because it's a collector? Are they harder to scratch? I'm assuming they stay sharper longer at least.
The $2500 is a collector's edition of some sort. The normal Sebenza's run about $400, and comprise the standard for quality folding knives.
Blades are like anything else; quality will only be distinguished by holding different knives and by what job you intend them for. If you rarely pull the knife out, a $15 Mora will do you just fine. If you carry and use a knife every day, why short yourself? What's a extra couple hundred dollars, in the long run? Better blades will have better construction, materials, steel, balance, grind, and ergonomics. Better folders will have tighter tolerances.
Just because a knife is low-end doesn't mean that it's complete crap. I never said that. I like my 5R Rem 700, but it's not a high-end rifle by any stretch of the imagination.
Here's a better comparison, and since you asked about EDC straight blades, more relevant. I have a RAT Izula, and I bought all my brothers Bark River Bravo Neckers for Christmas the year before last.
Price - RAT $55 with sheath, no grip; Bravo Necker $79 with sheath, no grip.
Components- RAT 1095 with powder coating, BR S30V with no coating on blade, powder coat on handle.
Grind - RAT is flat ground; BR has one of the nicest convex grinds you've ever felt
Edge - RAT is sharp; BR is shaving sharp. Literally, we were shaving patches of arm hair off with no trouble at all.
Overall - Both great knives, but the BR comes out way ahead. The 1095 of the RAT is a great, hard steel, but corrodes easily if not oiled, especially around the grind and etchings. Leaving this in the sheath wet is a bad idea. Have yet to see corrosion on the BR, but I wouldn't leave that away wet either. Both blades are scary sharp and hold an edge forever; however, the BR is easier to work with in general because of the profile of the blade and the convex grind.
The Bark River is 150% the cost of the former, but well worth it. I have owned and have EDC carried both, and have used for survival applications, chopping, batoning, and skinning. I have lots of other knives of assorted brands, most of them live in a box.