Erm.. what are you looking for in terms of costs? Like.. monthly electric bills because of the heaters, powerheads, lights, filters, etc.. Or maybe monthly costs of food, water, salt mix, replacing light bulbs.. ??
It's hard for us to give you a complete estimate without really knowing the scope of your question. You have to be specific, unless you want someone to answer a junkload of questions you yourself may not even care for.
I guess the most expensive part of SW
.. in the long run, would be the livestock. Coral, fish, inverts. A lot of livestock for SW
are expensive, with the exception of all the cheap fish and inverts, but that's usually never the case with coral. I have a hard time finding coral for under 20$.. but that's why frags were invented.
Second most expensive thing, would probably be food and salt costs. The larger the tank, the more salt you will need. The larger the tank, the more fish, the more food you will need.
Next most expensive thing, IMO
, would be replacing the light bulbs. Depending on the fixture you are running of course. But for me.. it will be around $50-80 depending on the quality of the bulb i intend to get. But i'm not planning on buying junky bulbs for my fixture, so i'll probably spend $70.
See where i'm going with this? The daily, monthly, yearly, and overall costs really vary from tank to tank, and from person to person. But in my mind, and from what i've seen so far, the larger the tank the more money you will be spending overall.