The thing about using iron pipes is that the fittings end up getting really expensive. If you go price it all out, a stand that's something like 6'X2' and 3' high would be over $300 I would bet. For example flanges that you would use for the feet end up being about $6-10 each depending on the size. For 1" pipe, and if you have 8 feet (every 2 feet) then you end up with 50-80 bucks just for the bottom flanges, not to mention all the T's and elbos.
I built a large computer monitor setup using iron pipe and I saved over $150 by welding everything. Unless you're doing something really basic, welding it is definitely the way to go, not to mention depending on how you build it, you may not be able to thread all the fittings.