Okay...
Having just spent 8 months in KU and Iraq...
And a month in Malaysia before that...
And 22 years in the field before that...to include American deserts, Alaska, Panama, and so on...
And having been in the knife industry for about a decade...
The bottom line is this from my "limited" experience -
They charge you extra $$ for only two reasons:
1. The finish any non-specific firm may be offering costs them X amount and they have to ensure a profit regardless. No biggie, that's business.
2. The finish same non-specific firm is offering doesn't cost any more than the other finish but is a marketing tool meant to take advantage of a popular theme or trend to make the buyer feel "special".
Field experience -
Said this for years in many mediums...
Black, tan, olive green, or hot rod primer gray it DOES NOT MATTER. The goal is to take the "shiny" off of SHINY in a high light reflective environment. The DESERT offers such an environment given there's NOTHING out there to block REFLECTION. This to include reflection off of vehicle and signal mirrors, exposed optical sights (I HATED it when I lost my front sight cover off my M4's Leupold CQT scope while in Baghdad

) and so on.
Flashlights, especially tactical lights, offer similiar problems. They can activate when YOU DON'T WANT THEM TO. I solved this potential problem by super gluing a blue lense cap / cover over my tac-light so if the light activated by chance or accident at least the beam would be somewhat subdued for the moment it took for me to deactiate the light.
Rex Applegate promoted a shiny blade over a subdued one for close in combatives. He believed seeing that momentary flash of steel could buy a critical half second of shock, fear, awe, and so on. However, I have maintained Applegate was talking specifically about a CQB knife and specifically about close quarters combat. Not about a knife that you used every day to cut tape, open boxes, or jimmy stuck shell casings in a highly reflective environment.
You want tan? Buy tan. You want black? Buy black. You want hot rod primer gray...buy a can of spray paint for $4.00 and do it yourself. The objective is to cut down reflection. It is not camoflage, and it is not "protective" of the blade's steel unless it is bonded to the steel and not merely painted or sprayed or coated over it.
90% of the time your knife is in its sheath or scabbard where the blade is obviously masked anyhow.
GW
PS: While editor of Fighting Knives magazine and in researching my books on bladeware, and in doing the field consultation for the 21st Century KA-BAR fighting knife for KA-BAR, I learned that any number of companies offer blade coatings simply because the competition does.
I've heard, from the horse's mouth, where firms simply dab on a coating and look for the least expensive such coating to "compete" with the guy down the block. "They wear down and off anyhow with use" is the common justification for a cheap but sexy cosmetic finish. One company discovered their current finish by ACCIDENT and went with it. Another company saw the finish and offered to purchase rights to it 'cause it was so "different" and "attractive".
The original company chuckled and said "no"...quietly laughing in the knowledge they'd stumbled onto their new finish and understood it was a fairly common such coating that took on the appearance it does due to something other than the properties of the coating itself.
Ah, ya gotta love it.
Cans of tan spray paint are normally the same price as cans of hot rod primer...plus you get to enjoy the sense of accomplishment that comes with doing your own work

.