Afghan, I don't understand what your fetish is for a thick knife. Honestly, if you think your Cold Steel knife is thick, pop on over and get a product from Himalayan Imports. You haven't seen beefy yet. A thicker BK 7 or 9 would alter the mechanics of the knife, and reduce their useability. That's been demonstrated repeatedly in this thread by actual knifemakers and other people that know considerably more than you.
Okay, first, price. Sure, you can look at street price, but that tells you bupkiss about manufacturing price. I can tell you in point of fact that thicker stock costs a good bit more in a number of different ways. For instance, for regular 1095 at Aldo's, you're looking at a $6 difference per 4' length between 3/16 and 1/4. When you add that up to enough steel to make a production run of knives, that's serious money for the manufacturer. You are only thinking about it from your perspective. You need to look at it from the perspective of a manufacturer.
But that's not the only cost for thicker steel. Because you have that additional 1/16", it's going to take longer to grind each knife. That's additional time that you're either running machines or paying workers or both, more steel wasted, and more value added in labor. Shipping costs increase for more weight, especially if you're shipping by palette to dealers.
Outside of cost, you also aren't thinking about blade dynamics and ergonomics. Part of what makes the 9 such a good knife is the way it performs for such a light weight. It competes with much heavier and thicker blades, especially with a convexed edge, and yet is thin enough to still perform slicing tasks, and light enough to reduce fatigue, and the point of percussion is perfect to grant it good power, but still nimbleness. If you change the stock weight, you're going to be putting comparatively more weight in the blade than the tang of the handle, which will move the point of balance and percussion by inches. That will make it a whole different knife, and one that sacrifices a whole lot of it's advantages and selling points for, well, what exactly? That's something you have yet to explain. You've been given a bunch of arguments as to why the thinner stock is better by some very experienced and knowledgeable folks, but you persist in saying nothing more than "thicker is better, I like my Cold Steel knife."
In fact, the only "argument" I've heard from you involves toughness, and if you do a little research and reading, you'll discover that a proper heat treat is the critical factor in that. Even an 1/8" knife can be more sturdy than a 3/8" knife if the heat treat and temper is done right.
If you really want a big monstrosity of a chopper, go get yourself an HI with a 1/2" blade. I can't really see why you'd even want such a thing, but to each his own.