Duketown Stingrays is where you'll get the best quality from. They breed some crazy nasty Albino rays, not just Pearls but also Hybrids (Henlei x Pearl Albino hybrids) and even more crazy stuff. Some very crazy pure Pearl patterns aswell, pure white Albinos, yellow/gold ones, red ones and so on.
From my knowledge a standard pair (the standard are the ones that are more red-ish) costs about 4k. Price obviously goes up depending on the quality, pure white or golden Albinos will cost more, the crazier the pattern is, the more they'll cost and so on.