It's really preference. Everyone told me the same thing with saltwater "go bigger" but I still prefer smaller tanks *shrug*. Less water needed, easier water changes. You just can't overstock. You'd be limited to a few small (2" or less) gobies or something, and some inverts. You can do soft corals and stuff though.
You really can't do clowns or damsels in a 10g as they get too large.
You are, however, wrong about changes not being as drastic in 30g. Water parameters generally change faster in a smaller tank than a larger tank. A little bit of evap in a 10g will fluctutae your salinity to a greater degree than a 30g, and you need to be vigilant with water changes and freshwater top offs.
The price is not going to be great for either tank if you're careful. But the cost for a 10 gallon isn't really going to be lower than a 30g, other than for live rock, salt, and sand since you need less.
The lights and filters for a 10g are going to be about the same as for a 30g, despite the tank being smaller. And in fact some of the nano stuff that works good on a 10g might be more expensive than the standard equipment that would fit in a 30g or larger. And you're still going to have to buy test kits and a refractometer and such for either tank, which is going to cost the same either way.