it turns out you only get two shining cards per booster boxI'm still wondering what's the pull rate of a star card from the booster box... :/
I was looking on buyee and at saw that a guy had shiny cards for about $35 a piece
That definitley seems to be the case. I have been observing auctions for shining cards on buyee and currently there a a few listings that are sitting at at most $5.00 with about 23 hours left. The gxs from the set are going for more especially the SR GX mewtwo. That pretty much confirms that shining cards are rare but not GX rare.