Tank aside the bulk of the upfront cost for me was the following:
Lights... This one is a biggie. If you are planning on keeping corals/inverts you will need lighting. This can get expensive quick depending on what you need. You could ballpark 300-500 easily if you plan on keeping corals.
Live Rock... For me this was a huge expendature. I went with all cured live rock. I slowly upped my figure. The estimated amount in #'s is 1-1.5 (closer to 1.5) per gallon of water. Most LFS charge $6-8 per pound. Some will carry it a bit cheaper, some a bit higher. To reduce this large up front cost you could go with a % that is live and a % of base.
Substrate... This isn't to bad. I went with 2 bags (about 60#'s) of Aragonite. I think it ran around $25-30 a bag at my LFS.
Salt... This isn't to bad about $40-50 per container.
Water... RO/DI units are highly reccomended for long term success. This range from $150-300 for most units.
There are several other things.
Filtration, Skimmers, QT Tanks, Test Kits, Hydrometers, etc.
I ended up building a sump shortly after the start of my tank so that I could also have a refugium. So you have to factor in $100-200 for the pump, overflows (if your not predrilled), etc.
It adds up pretty quickly.
For my 75g from start to finish I easily spent several thousand dollars.
http://www.aquariacentral.com/forums/blog.php?b=21
This is Grins list for what you will need so that you can price it yourself. =)