Skimmer reef octopus ns 80
Sand (rough guess) $15
Light (to support corals, rough guess) $65-$100
Dry live rock $20
Salt for 10 gallons-$10 instant ocean or $15 reef crystals
Before any corals or fish I'll say $150 to $200 in setup cost, completely rough guess, depending on things you do or don't have it will be more or less. The desire for corals drives the build price up, without need of them you could do it for 80 or 90 bucks.
That said a 10 Gallon sw
isn't easy to maintain. The startup cost you would save by using a 10 vs a 20-29 gallon will disappear in the first year. My first sw
tank was a 20 high, a 20 long would afford a nice buffer against swings compared to a 10.