how much are action figures at G fest?

I've never been to one, so I don't know. :T

It depends on the quality of the toy.

If its a bandai gashapon, or a S.h. Monsterarts.

Like say there is a X plus Burning Godzilla, and a Bandai Muto. The X plus is going to range from 300-600 dollars, while the bandai muto will range from 12-30 bucks a piece.

Or if its a Atomic roar Godzilla, vs a S.h. monsterarts Godzilla 2014. The Atomic roar will go from 3-6 while the s.h. will go from 60-100 dollars a piece.

This is like asking "how much do cars cost": it really depends on what you're looking for.

If you're looking to get something from the 2014, you'd pay a little more than you'd pay for in the store. I'd you're looking for a rare vinyl from the 70s, expect to pay several hundred dollars.

In my situation let's say for example the Bandai Japan figs

Well again, what Bandai Japan figures are you looking for? Some are more rare and expensive than others. For instance, Movie Monser Series Jet Jaguar goes for like $10 while something like Memorial Box Godzilla 1985 can easily hit $80-$100.

G-Fest Prices, anyways, are generally balanced. Everytime I've gone, I've found figures that are the same as their list price online, some a little bit over, and some a little bit under. It really depends on the dealer and the figure in question. You more-so just have do depend on luck when buying stuff there (first find what you're looking for, then determine if there are any other dealers selling the same figure, then determine who's got the best price, all while doing this in a timely matter to prevent the figure from disappearing from stock).

^Pretty much that.  As a veteran of five G-FESTS, I've come to learn that the prices are pretty much balanced, and that its like shopping on eBay in person.  One suggestion I can make for next year... scout several tables for the same item before buying, so you get best deal.  Some tables sell things for more or less than another, and it falls to you to see the quality of each figure to determine which one you want.

Another helpful hint... always save a little money for the last day, so you can haggle!  The sellers want as much of their stuff gone as possible, and I've gotten some serious discounts (including a free CD this year!) by waiting and haggling on Sunday before the dealer's room closes for good until the next year!