That is a very collectible patriotic button! There are several varieties of the snake button and I have seen that one dug in the SC/GA also. Value not as much as that ebay price...listing prices are fantasy prices usually, and did not see a sold version. I have two other versions and prize these buttons. Value wise...it would depend on the buyer. I have seen some sell for several hundred dollars. Go to a Civil War show and sale or google Patriotic buttons sales... you are bound to find one for sale and get a good estimate.
Very Nice Find!