Yes, you can get 3" of K390 for $70, that's irrelevant to this discussion. We're talking about a fixed blade at 18" overall length, that's $100 just for the barstock if you're shopping for high alloy steel.
The 12" Warcraft Tanto is practically running into the design territory of swords and in that industry they almost never use steel with more than 0.5% carbon.
If you want a big knife to beat on then 4034 is practically ideal, you won't find anything better.
Personally I'd prefer 14C28N but that's still a compromise on toughness that I'm personally willing to make, for the average user it's really hard to argue against 4034.
The only real question here is why these knives are priced the way they are.
Are you seriously comparing plain carbon steels with modern super steels and alloyed steels?
And no, 5160 has more than 0.50% carbon.
1080 - the same
1075 - also over 0.50%
80CrV2 - around 0.80% on average...
And that is IF the smith is using plain carbon steels. So smiths ARE using the steel with more carbon than 4034 garbage, despite the fact actual swords are much longer than this POS.
Cold Steel Kukri at lenght and thickness simply does not enter tne sword category, meaning they COULD or better said SHOULD have used an actual high carbon steel, and not medium carbon steel.
Speaking of average user - an average user won't spend that kind of money on a knife!
And except toughness there's also a thing called yield sthrenght, meaning the maximum ammount of force material can take without permanent deformation.
Silly putty is tough as hell, sure, won't break, but also won't hold up to anything.
So theoretically, 4034 is tough, but will bend... 14C28N is "less tough" but won't roll or bend as easily, and will actually hold an edge.
Take a look at Extrema ratio, they use high carbon stainless steel for large knives that hold up to actual hard use, and will hold the edge for long.
There is no real justification for either using 4034 or selling it at such price, except good old greed... real reason is "we think our customers are dumb and we like money"