WallyWorld generally has air suspension secretarial chairs with arm rests starting around $25. Throw a drop cloth over it if you don't have windows to keep the rain & snow out of the blind.
I picked up a couple of those tri-fold padded soft stadium type seats with the side straps which hold the back upright. I'm not sure what they call them but they look a lot like Thermarest mattresses with side straps which function as the back support.
They are great for a blind or stand. You can set them flat on the ground, they are light, very comfortable (careful you don't fall asleep), will keep you dry, and they fold up into a package just a bit larger than a boat cushion.
These are easy to find and generally only a few dollars in the second hand stores.
Oh yeah, though the basic ones are $6, the camo ones are $9.95 if you want to really splurge instead of getting a plain brown one. Sure, you can find them for $24.95, but look around and they'll be $10, maybe $15 tops. Don't pay more than that!