I'm building one right now, or more accurately reworking/refurbishing an old one. The original owner made it from 2" 11ga. square tube of about 4' x 6' dimensions on a 10' tall stand made from 3" x 1/4" wall square tube. Heavy as heck!

He made the original front 3-facets, so the blind was actually a hexagon, and he sheathed it all with 1/2" plywood. It's lasted 8 years and was in rough shape. Plywood doesn't weather very well, and he had lots of exposed ends that allowed the water to penetrate the ply's. In addition, the half assed attempt at windows, left them prone to leaks, blowing open, PITA to open etc.

I've cut all the steel apart and made the blind a true 4' x 6' rectangle. I then framed for the door and windows using 1 1/2" 14ga. square tube and sloped the roof. It will get fitted with (2) 30" x 11.5" slider windows on the front, a 30" x 11.5" slider on each side and a 16" x 11.5" on the back, with a 24" x 60" door also on the back. All the doors and windows are from Deerview Windows and cost $552 total. These windows/doors mount from the outside and seal and cover any end grain of the window/door openings. I've used the same windows on some other blinds and they're top notch. I put a carpeted rest under each window, so your gun isn't resting on the metal window frame.

The blind will get sided this time with 7/16" LP siding panels. These panels have a surface coating/primer that holds paint and weather very well. The steel frame, interior and exterior will all get painted with Rustoleum oil based paint. BTW: equal parts of Rustoleum Rusty Red Metal Primer and Hunter Green Gloss paint make a perfect Satin Olive Drab color that goes on easily, lasts a long time and is easy to recoat/touchup. The outside blind corners will get painted galvanized 2" corner flashing to cover the corner end grains (the galvanized trim will get rubbed with vinegar to etch to hold paint). The roof will be shingled with appropriate drip edge.

The key to making homemade blinds last is using siding, not plywood, protecting all end grain and using good windows/doors.

This blind will get mounted on a 3' tall stand with skids (runners) and can be dragged on/off a trailer. It will get anchored when in place to prevent blow over. It will have steps/handrail to get in/out.

Estimated material costs:
$200 steel (1 1/2" square tube for framing the windows doors and a 20' stick of 2 3/8" pipe for the skid base)
$552 windows doors
$50 for self tapping/sealing screws and other self tap flush screws, tube of brown silicone caulk
$285 for LP siding panels
$100 for floor roof plywood
$40 shingles
$60 corner/roof flashing
$66 paint

$1350 total (Some of the steel from the original stand I was able to re-purpose, or I had as scrap/drop for the stairs etc.) Right now, I have 16- 20 manhours in 100+ degree heat building this thing by myself, but a good chunk of that was reworking/squaring the original steel. I have all of the framework steel completed and painted. I figure an additional 16- 20 manhours to complete. In reality, using square tube adds a bunch more labor to the welding, versus angle iron. But your fasteners aren't all poking through on the inside like angle iron.

When I priced material as above for a similar blind as stick built, material cost was $1100. But the labor using a chop saw/framing nailer etc. was probably 1/3 to 1/2.

Pricing new blinds (without a tower) would be $2300, figure with tax and building a base, you're looking at $2750 plus some of your time to fab the base)

In reality, I'd buy a good quality fiberglass blind from Dillon or Xtreme Blinds. and build my own base. Unless you enjoy/have time to build one right.

Half the reason I'm into this project is to keep the costs off the radar of my BIL's wife. He can hide $200- $300 expenses at a time.