Neither are purebred Ameraucanas.
One classic characteristic of EE's are green legs. Not all have green legs, but most do.
Ameraucanas have slate coloured legs - here's a link to pics of Ameraucanas from the National Club.
http://www.ameraucana.org/scrapbook.html
As for how much a 12 week...
Ameraucanas are a purebred breed and only come in 8 colours according to the SOP (standard of perfection).
Easter Eggers are usually Ameraucana or Araucana crossbreds who lay a coloured egg - the colour can range from blue to green to even pink hued.
Purebred Ameraucanas are only sold by...
They aren't Ameraucanas, they are Easter Eggers.
$4 and $6 is very cheap. I only buy birds that are over 12-14 weeks old, that way I KNOW I'm getting pullets, however, I do have to pay a lot more for them.