re: Salt water fish tanks

It all depends on what you want to keep. I had a 170 gallon that I had around $8k in. I'm in the planning stages for building another one next year, much smaller though. It will only be 50 gallons and my budget is between $1500 and $2k. I want to keep stony corals and clams, will be lit with LED lights. I want all pumps to be silent and efficient.
You pay for good equipment with this stuff.

Maintenance wise, it will take some time to get the chemistry down and understand your calcium demands and how to accurately supplement for it.
Other than that, it's not a lot. Weekly or biweekly water changes, clean your skimmer weekly, clean pumps every 2 or 3 months.

It gets easier as you go. In the beginning there's a steep learning curve and that's where the majority of the work seems to come from.