You need 40' of stainless 2x2" square tubing. Depending on where you find it and what you can do by yourself, I'd expect to pay at least 400 dollars for the SS tubing. Everything else for the build can be found by scouring EBay and these forums. Since you are welding a frame, can you weld, or do you need to hire a welder?
If you are following the actual Lonnie Mac Brutus Ten build the article has a parts list and prices, albeit from 2007. The thread below has a lot of discussion as well as some price information. As far as budget it depends alot on what you have available already in the way of equipment. If you have kettles, butners, tubing, valves, etc. and you can implement into your new stand then obviously your costs go down. If you are building entirely from scratch including kettles, I would budget at least $1500, although several members here, myself included had this discussion last spring when we were building them and ran well into the mid $2500 range. I have my exact number on a parts list spreadsheet at home. PM if you want it. Of course, the harder you look and the more you can do yourself (welding, electrical, etc) the cheaper.
Steel is much more today that it was when Lonnie built his. Even cold steel is higher price and stainless is downright ridiculous. Although if I did again, I'd probably consider stainless. (Powder coating is a waste & expensive). Use high temp primer and paint instead..ok sorry, I am getting off topic.