guys that weld with c02/argon mix

We got our co2/argon tank ( I think it's medium size) from a welding distributor in the town next to us, it was a 99 year lease/with filled bottle for like 140.00 but I think that was at least 10 or more year's ago. If that's the quote for 350.00 man that's just incredible for the price of this stuff! Like the previous guy's said..... never put any gas in a container that it is not intended for, as the bottle's they sell are totally identified as what's in them.
Like I said above, 99 year lease on the bottle, so I know we won't have to renew!!!!!!!!!!!!! lol.