Well, I've never heard of Ice Mew or Mew lv.X (maybe your thinking of Mewtwo lv.X)-So that means Mew ex must be the rarest of your "3".
Here is what Ebay sellers think it is worth: so about $15 or up. http://www.ebay.com/itm/MEW-EX-100-110-Ultra-Rare-Holo-Foil-Star-Pokemon-EXL-PL-/230659070827?pt=LH_DefaultDomain_0&hash=item35b45a1b6b#ht_1330wt_167