I purchased a set of Oxygen & Acetylene tanks yesterday from a LWS (NexAir). The guy gave me a good deal 80&70cf tanks for $300.00 plus tax for owner bottles. I actually got new tanks! I asked him about the Gas Pony deal, and told him I had thought about going that route, because of weekend and late night exchanges. He admitted that was their selling point, because their tanks are high. It would have cost me about $500.00 for the bottles through Tractor Supply. He went on to say the D.O.T. busted Gas Pony, Tractor Supply, and Northern Tool because they were filling other companies bottles. Airgas went after them with a law suit, and pushed the issue. Apparently you could pay an exchange fee to swap your bottles for Gas Pony bottles, and they would trade whomever's bottles you had.