It is important to remember that saltwater tanks usually require substantial start up costs to create an effective system. Here is an example of start up costs for a 65 gallon reef tank.
DSA Rimless 65 Gallon Tank - $499.99
DSA Black 65G Stand - $399.99
Overflow Plumbing Kit - $79.99
Eshopps ADV-100 Sump - $279.99
ASM Mini G Protein Skimmer - $199.99
Aqua Excel DC6500 Pump - $204.99
2 x Kessil A160we - $239.99/each - note this lighting will support any coral growth
2 x Kessil Gooseneck - $35.99/each - mounts for light
Kessil Controller - $104.99
Portable Refractometer - $49.99
2 x Caribsea Oolite 40 lbs - $39.99/each
Live Rock - $3.99/lb - recommend at least 1 lb per gallon
API Master Test Kit - $24.99
Premixed Saltwater - $1/gallon
This is a list of the most basic necessities to start a nice reef tank. There are many add ons such as an auto top off, powerheads, dosers, reactors, and other equipment. This is simply an example - there are ways to cut costs if necessary - but it usually good to have several grand set aside for a reef tank. The good news is most of the equipment lasts 3-5 years and many quality items will hold some resale value if you ever choose to upgrade.
Small tanks are cheaper to start up, but they are more difficult for those looking to try out saltwater for the first time.
Here is an example of starting a 3 Gallon Picotope Reef Tank:
Picotope 3 Gallon Aquarium - $64.99
Live Rock - $3.99/lb - we recommend 1 lb per gallon
Caribsea Hawaiian Black Live Sand 10 lbs - $19.99
API Master Test Kit - $24.99
Premixed Saltwater - $1/gallon
Portable Refractometer - $49.99
Upgraded Wavepoint 6" light with blue & white - $57.99
Additional Items you may want to get when purchasing a new tank:
Heater - $25 - $40 depending on size of tank
Fish Net - $4 - $8
Cycling Bacteria - $11 - $20
Reef Mature Pro Starter Kit - $ 35
Auto Top Off - $149.99
UV Sterilizer - $130 - $200
Chiller - $200 - $600
Doser - $100 - $400
Powerheads - $40 - $600
Automated Control System - $250 - $800
Filter Medium - $10 - $50
Refugium - $40 - $150
As you can see, there are many items available for new systems so it is difficult to give an exact figure for new tank start up costs. It is best to figure out your budget and try to work within it.