The differences between a 10 gal and lets say a 55 are... price of lights, tank, skimmer, amount of salt, amount of LR, number of fish, number of powerheads, size of filter if you have one, heater size if you use one. So while both small and large setups are going to be pricey, I'd say the 10 is cheaper. However, once you get going on the 10, you'll want a 55 or larger in no time. My suggestion is go at it slowly. Buy a 55 or larger tank and sand. Build the system as your checkbook allows. You don't have to buy everything at once.
I have a ten and enjoy it. Here's what I've spent so far.
In $$
10 - tank
15 - salt
40 - Live Sand
50 - Live Rock
60 - Light - 28 watts
20 - outside filter
15 - heater
20 - test kit
13 - Hydrometer
10 - 2 damsels (rid them after cycle and now have 2 clowns
35 - 2 percula clowns
10 - 6 hermits
10 - emerald crab
13 - feather duster
15 - food
25 - Live Rock with Polyps on it.
30 - miscelaneous
So about $360 so far.. No skimmer - yet.