That's not true. You don't need to spend hundreds of dollars on lighting/fixtures.
Go to thatpetplace.com and check out the light bulbs. All you really need is a good shop light, the kinds you can get from Home Depot or Lowes, get either a double 36" or 48", that should run around 50 bux or so. You can get a protein skimmer for about 30 bux...depending on how fancy schmancy you want it.
The only thing that is the real cost of SW setups are the salt, live rock and of course the fishes. Depending on your taste of fishes, SW fishes are pricier as opposed to FW fishes.
Some other things you'll need is a good SW test kit, a salinity meter/reader (hydrometer), crushed coral (buffer the SW to higher PH). If I'm not mistaken, SW pH is around 8.0~8.5...its been over 15 years since I had a SW setup.
Other than that...you're pretty much set. As long as you get your tank cycled, which having live rock will help immensely, you should be able to have your tank up and running with a few weeks. I'd say if you can afford to get a lot of live rock, thats the way to go, but remember the more rock/crushed coral you have, the more water is displaced.
Oh yeah, one thing I see you're in NYC too, I'd stay away from Petland shops...stuff is way overpriced and they don't really have much of a fish collection...whether its FW or SW.
A nice shop to visit is out in queens, fishtown usa has a good selection of fishes. I don't know how old you are, but thats the last of the fishtown usa stores in NYC. I remember the biggest one was down on Chambers St., where you can walk in one side and come out the other side of the block. Now that was HUGE.
Another decent shop is a small LFS, its located on Delancey Street, Pacific Aquariums...nice picks of SW, but check once a week to get some deals.
A few clowns, damsels and maybe 1 or 2 cortez angels you'd have a nice lil killer SW tank.
Good luck.