Actual progress update:
I went out to Home Depot with my gf and bought the MDF.
5/8" Threaded Rods cost the exact same as through McMaster Carr, but 3/4" rods were $1 more each. The rest of the hardware wasn't even close. I'll be buying through McMaster Carr for the hardware.
I got several responses back about MDF pricing. The one local lumberyard that was able to give me a quote on MDF only had 3/4" (I asked for a quote on both 5/8" and 3/4"). Their quote for two sheets of 8'x4' MDF 3/4" thick cut to my design was a little over $80 with tax... a little more than I wanted to spend.
Home Depot's e-mail response was to contact a store in Louisiana. Confused, I e-mailed back asking why I should call them when I filled out their form with my location for the original question (even finding out the store number from the closest location for the form). They sent back a response that the Louisiana suggestion was a mistake, but I would still have to call the local place directly to get a quote. Since I wanted to check prices on the other ~6 items I wanted anyway, I decided to just go there and find out.
At Home Depot, I checked out all the hardware and was unimpressed by the pricing. One of the threads I read on Flexy Rack design stated that threaded rod was available in the plumbing section for very cheap compared to other locations where it was stocked in the store (several locations with the same exact item?).
Anyway, no threaded rod in the plumbing section and I determined that the only thing I wanted to get there was the MDF.
They only had 1/2" and 3/4" MDF. The 3/4" looked very nice and it was $27.37 per sheet.
We brought a 5/8" and 3/4" rod over to the MDF and decided that it really looked best to keep the Rod size as thick as the MDF, so 3/4" Hardware for the rest of the project was decided upon (although at this point, I haven't bought anything, so I could change the plan if I want to).
We got out two sheets and headed over to the cutting station where it's 3 cuts free, then 25 cents per cut.
I had printed out a plan (printed to full page) of what I wanted from the sheet
http://pics.bbzzdd.com/users/Y...wsDAjello/MDF_Plan.png
Cutting ended up being $3.00 to get twelve 26"x20" shelves and I have four 20"x20" squares as leftovers... maybe rear speaker risers if I'm in the mood for another project?
http://pics.bbzzdd.com/users/Y...wsDAjello/MDF_CUT1.JPG
http://pics.bbzzdd.com/users/Y...wsDAjello/MDF_CUT2.JPG
http://pics.bbzzdd.com/users/Y...wsDAjello/MDF_CUT3.JPG
We went to the checkout with the $3 receipt for the cutting and the woman at the register rang it up and said "Three Seventeen". I looked at her in disbelief thinking she meant $317.00
I said "how much?"
She said "Three dollars and seventeen cents"
Thoughts of morality flashed through my head as I hesitated for about half a second and then replied "That doesn't include the price of the material, that's just the cost of the cuts"
She asked if the boards had a bar code on them and I said I didn't think they did. My gf said that the two whole 8'x4' boards were about $27 each.
The woman found the item in the computer and rang it up.
"Thirty-two dollars and four cents"
I thought again... that seems awfully low, but I'm going to go with it. As I swiped my card and signed, I wondered why it hadn't been the ~$65 I was expecting. By the time we were heading out the door, I had figured it out that she had only charged me for one sheet of MDF instead of two.
Morality again...
So anyway, I'm planning on 3/4 hardware for the rest of it. Nuts and especially washers were ridiculously expensive at Home Depot. I think I might skip the acorn nuts on the top of the rods. Considering that adds about $20 to the cost of the 3/4" build, I think I'll try to find a better / cheaper solution. Maybe I'll use a few of the extra 93 plastic feet I'll have.