I know this has been previously discussed but couldn't find it using search.
I was in Atwood's in Sapulpa today and saw some Made in the USA really thick wall smokers. The wall thickness of the cooking area was at least 1/4". It is unlikely they would either burn or rust through for a very long time.
I found their website:
http://www.horizonbbqsmokersstore.com/servlet/the-Smokers-cln-Backyard-Style-Smokers/Categories
My wife had mine made by the welding / shop class at Broken Arrow High School a few years ago. Actually, I believe one of the teacher's made it in their spare time. They used 1/4" thick steel. Mine looks very similar to the 'classic' in the link below. It was a present from my wife but don't believe it cost any more than $350.
Get a piece of schedule 40, 24" pipe, and a piece of 1/4" plate for end piece. Cut, chop, shape, weld. Last forever.
Atwoods gets some pretty cool stuff from time to time.