The windsor a around here do in fact sell rough lumber by the bd.ft. And the walnut I mentioned comes in various widths. $6.99 a bd. ft. That's for 4/4 though. And for shorts (Less than 8' long, usually less than 6' long, maybe that's what you meant). Not sure if you're getting 8/4 for $8 or what.
I agree though, Windsor is usually quite expensive. But their price on shorts is good.
If you're ever on the island, western maple is pretty common air dried from local mills. I can give you some numbers to guys selling for $1. But of course, air dried means you need to let it sit a bit. Pain in the butt.