Wow, awesome! I don't really get it, though. How could you get it for $1?
I work in retail, sometimes we mark things down to 90% off. After a certain time on the sales floor with no one buying it, things come down to a penny - at that point it will ask you for a price if you scan it. You are supposed to sell it for 90% off the original price when it gets to that point...anything less and it should be sent to the surplus company.
I guess if they store used the tank as a display, then they could sell it to you for $1 since it has already been accounted for...