My LFS store is awful I agree. Many things are marked up well over 500%. Not to mention tax is 8% here.
And you right it would cost that much here for you setup. I agree you got a great deal as well
Edit: For reference a 125 gallon tank was on sale last year for $250 at it lowest price, which over half off...Just for the tank.
Tank prices are high here as well, at some point I would like a 125+ gallon tank, but its crazy the cost to set up it new, and some of the prices on Craigslist are not exactly cheap either.
Just some examples on Craigslist right now a 60G set up for $600, a 29G set up for $200, 90G bowfront $2500. These are all full set ups, tank, stand, filter, lights, average price for a 55G is $200+ There are also good deals though, a few months ago I saw a 150G tank only for $0 (wish I could have gotten that one) one ad is for 8 tanks (5 x 40G breeder and 3 50G breeder) for $40, again tank only. I got a 29G set up for $75 last year and felt it was a good deal.
I think the OP got a good deal.