Actually, Shinings from the older sets (Neo: Revelations, Neo: Destiny) had about the same rarity as a normal holo. Same with Dark Raichu in the original Team Rocket set, and other secret cards. The new Shining Pokémon (EX: Team Rocket Returns onwards) generally come anywhere from 1 per box to possibly 1 out of every 3 boxes.
WotC was rather mean to make the rarity of the old shining cards the same as regular holos. From what I understand, the shinings in Neo 3 and Neo 4 in Japan were extremely rare, and generally were valued $50 and upwards. Old Shinings outside of Japan seem to go for as high as $20, but rarely higher.
I've seen an eBay auction where Shining δ Charizard was going for $60 with 114 bids, so as I expected, it is a valuable card.