How much royalty do artists get from each 99 cent download from iTunes? ($2.50)

There is no fixed royalty and no official information. It is the
record companies that makes the deals with Apple/iTunes. The amount of
money the artist gets depends on his/hers contract with the record
company.

If you are an independent artist and would like to have your music on
iTunes you can, for example, sign up with cdbaby.net
(http://www.cdbaby.net/dd) who will then get your music on a number of
distribution services, including iTunes. The royalty you get from them
is 59 cent (they get 65 from iTunes and keep 9 % of it), MUCH more
then any signed artist would get.