This is a good point, but it wouldn't necessarily take a new skill to cause the crash. A big new tradeable weapon could do it. Anything that would cost a lot of money could do it. In fact, even a revision to an existing skill could do it. For example, what if Jagex released some beastly new high-level prayers? Players would start scrambling to buy dragon bones, which would skyrocket in value. Even this could trigger a dumping of partyhats. The higher the hats go, the smaller the stimulus that will be required to set off the crash. They become more and more unstable as they climb higher and higher. Or they could use the bones as a bartering tool to get partyhats :o?(Just like when the herb update came out). That's another possibility, although i do think the lower 3 partyhats are leaning towards the outcome you stated.