per foot basis is really not the best way to compare rugs as a consumer. Buying agents sometimes use per square foot as a unit of measure, but this is for comparing : two rugs of exact same wool, with nearly identical thread count, with exact same design, made at the same time by same manufacturer.... you get the idea - all in different sizes. You have to be very seasoned in rug knowledge to do this.
if you want to get a better handle on values, I would use the rug estimator
http://www.rugrag.com/Ap...Viewer.aspx?FormulaID=11 I would not compare two different rugs by just knot density and square foot price. Values of two rugs vary too greatly to simplify in this manner. In my opinion, you would be misled to figure value in this manner. Especially with rugs showing use or two rugs made at different times - you would be very misled to not account for variables as one rug to another by square foot price. Buy the rugs you like, and buy them from reputable dealers.