I got some cotton/poly ripstop Propper khaki bdu pants for about $12 a while back off the Internet. Store must have been having a loss leader sale.
Thought on why khakhi's may be a little heavier than other "Mil-Spec" BDUs in solid color. The Feds do in fact buy and issue solid khaki BDUs, so these may be the real real thing, and other solid colors are not in fact GI in all respects (not maade here, etc??) since they aren't potentially for a gov't contract. Just a thought. Worth what you paid for it.
If you are looking for pants similar to bdu's for knock around or work, check out Kohls. They have a Columbia Sports pant that doesn't have all the pockets, but does have a few extra in convenieint places, they also had a few "cargo" pants that most to all of the bdu type pockets, some with snaps, some velcro some button. In any case I got a few for wearing to shoot, camp, etc and knock around because the jeans I inherited from my Dad when he passed away were wearing out. They ran about $15 to $25 on sale and seem to be holding up real well. They aren't "real" bdus but for rough use they aint bad and come in a variety of grey, green or tan khaki colors. They aren't Levis or jeans but they sure are comfortable. And they were much nicer than the "painter" pants.