And to add to what @littlebigreef said, the reason that many zoas are expensive is because they are hard to grow. I have several cheap zoas that I love way more than something like a strat, but the reason they're cheaper is because they're easy to keep, grow fast, and are easy to frag. That leads to more of them, which leads to prices going down. Same reason that zoas like Exospheres used to be so expensive and aren't now.