Very wierd,, I bought this same model from this guy and it arrived this past Friday night.. It works awesome ! very hot... it even opens from the top on a hinge so you can do mtce or cleaning... If you want a ready made forge with no messing around ... then BUY one !
I started to get a list of everything I needed to make a decent one and then called around to get the soft firebrick and once company wouldn't even ship it because they have had too many problems with them breaking.. Once I realized the cost of getting all the bricks, steel, tubing, fittings... and since I just bought a wire welder and am pretty bad at it.. I just went ahead and bought one... .. Get one, you will be happy....
Also, if you are good with welding and have access to cheap or free steel, and can get firebricks locally... you can build one a lot cheaper.. but then.. will it work ?
Good luck !