How about $1.15 per linear foot for 16" deep shelves? I just finished a project similar to this. In my garage I wanted cheap, strong shelving, 16" deep with a minimum of support structure, for storage of heavily loaded flip lid tote boxes. Basically, I drove 20" lengths of rebar into a series of holes drilled in a horizontal line in all studs of the wall where the shelves would go, and laid 7/16" OSB on top of that as shelves.
The details:
I cut 20 foot lengths of 1/2" rebar into 20" lengths (using a SawzAll). Used a laser level to project a horizontal line at shelf height and a Portalign drill guide to make sure I was drilling a 3" deep hole at right angle in center of every stud at the horizontal laser line. I sank each rebar 3" deep into the 2x4 stud. The 1/2" rebar is actually a bit oval shaped, slightly larger than 1/2" in one plane, so I used a belt sander to shape 3" of the end of each rebar into a more circular shape, and I relieved the sharp edges of the cut end of the rod so it would slide into the wood without catching.
I lubricated the insertion end of the rebar with Dove soap to make it slippery and drove it into the holes using a 3lb dead blow plastic hammer. I marked the rod at 3" so I would know when to stop driving it - otherwise you could drive it entirely through the stud and into the adjacent room. I know that by having done it.
Shelving material is 1/2" wafer board (OSB). I cut three 16" wide shelves (8ft long) from each 4x8 sheet of OSB. I laid the OSB on top of the rebar and joined the butting ends of shelves together with nailing tie plates (StrongTie HTP37Z) and 1/2" truss screws (underneath).
In spite of using the PortAlign, some holes were not 90 true and there were minor variations in the true level of the rebar sticking out of the stud. For garage storage, I did not bother to correct the issue. Although I could slip a pipe over the rebar and bend it to be level, the variations were relatively minor so I didn't bother.
Each 16' shelf is now loaded with 12 gallon flip-top tote boxes, each weighing about 40 to 55 pounds, for a total weight of approximately 600lbs per shelf. They are placed on the shelves so the narrow end faces out and they actually hang over the front edge of the shelf a few inches. One wall of my garage has 6 shelves, 16 feet long so the total wall load is 3,600 pounds.
This shelf system cost me about $1.15 per linear foot (in 2013). It's not completely rigid - with the loading described earlier, the front edge of each shelf deflects downward about 1/2". The shelves bounce up and down slightly when putting boxes on them.
A structural engineer would probably not be happy that I drilled six 1/2" holes 14.5" apart in the studs of a support wall, and then loaded one side of that wall with 1.8 tons of weight.
If I was doing this for decorative shelves indoors, I'd probably use plain steel 1/2" rod which is more rigid than the rebar. Rather than trying to drill a hole edgwise into a thick shelving plank, I'd probably rout matching grooves in two boards and then face glue them so the grooves face each other and form holes to be slid over the rods sticking out of the wall. Obviously, price is increasing dramatically for this option.
Several times I had to remove rods that I had already pounded into the stud. I grabbed the rod with a large ViseGrip and pounded the ViseGrip outward with a dead blow hammer. It's imperative that the rod end has been lubricated with something like Dove soap to make it easy to insert and remove.
Obviously, this shelving system is not adjustable - or at any rate, I would not advocate drilling 1/2" holes every two inches up and down studs in a bearing wall in order to provide "adjustable" spacing.
It should be easy and cheap to do this for an 11" shelf, and probably the rebar would be plenty stiff in such a short length and less loading. I would advise using every stud you can locate.
...but my garage is on an ultra cheap budget. These shelves were built out of 2x4s and plywood, nothing else.( okay okay, trim pieces are $2 furring strips). Also, paint helps
