Dang, if you think shopping around makes you out of line, you must be a saint and a good neighbor to have. Lol. I would have done the same thing. You should have been grandfathered in IMO.
On a side note, $400 for 50 gallons.. ouch. Paid $1.25 a gallon here and filled our 500 gal tank.
What do you use it for anyways? Makes me wonder if you could get some oversized cylinders and fill them yourself.