They used to be common in the hobby but from my understanding in the mid-90s until recently, most of the areas where they can be collected are under control of various paramilitary groups and narcotic trafficking organizations making collection impossible. As such they're now rarely available and command high prices when they are. I believe the lowest I've ever seen them for sale was for $650 USD but more often I see them for about $900 USD. Though I don't recall how big they where at that price.