For what it is worth....I got a 32gal s/w aquarium in April 2000. I would say that I am cheep and hardly spend much on my tank. None the less this is what it costed me over the last couple of years:
2000 = $642.23 new lights, filters, live rock, etc. The fish were the cheapest part except the tank which was free
2001 = $ 88.40 I can't believe I spent so little.
2002 = $153.78 new heater, new lights, new test kits, etc.
2003 = $406.31 I started to add coral to my tank...
Even a medium tank 30-55gal is cheap compared to the maintenance costs.
But Hookman is right it is well worth it.