Okay....
Skimmer (Deltec MCE600 second hand) $650
Salt (25kg Red Sea) $130
Pumps (Streams - TS24 kit) $1200
Rock (live rock) $450
Sand (coral sand from jansens) $50
Refractometer $100
Testkits (salifert pH, ammonia, nitrate, nitrite, calcium, phosphate) $180
Rowaphos $50
Kalk $40
Tank+Stand $1400 (aqua one R2 - 150 - 5' 100Gal tank)
Lighting $900 (2x250W mH pendants, still need to buy the 2nd one)
Total: $5150
Given you could get a tank+stand for cheaper, say $500, you're looking at around $4250 - nice estimate
Now.. that's not including any livestock, I tend to leave that out of "setup" costs, since you can save for that whilst you watch your tank cycle/mature etc.
I started with a couple of Seios ($240), and decided they just didn't flow enough for what I wanted (there were lots of dead spots etc), so I got the streams, knowing they'll handle a larger tank in future etc. For the record, the Seios were silent, started every time and never gave me any issues