Spyderco Endura 4 meets your weight, width, price, but not size limit. It is just under 4 inches.
Carrying a 6in folder is plain crazy (my opinion here folks). I used to sell the 6in ti lite. heavy, need 2 hands to get a good grip on it, and very unbalanced. I don't know what you need a 6in folder for, but you must work in very extreme environments, or its your last resort when playing with grizzly bears. Most 6in folders will not meet your weight or price requirements, and they will be very awkward to wear in your pocket. Plus, if it even is legal, pulling it out in public will either make someone scream, or call the cops.
My suggestion, either go with a fixed blade, or go with a 4 inch blade.
Good Luck