when they were first released?
Now pretty sure everyone on the game has had a phat set due to the xmas event, also jagex said they will be returning, so possibly every event there will be santas/phats/masks, etc. it just wouldnt work so there's no point in waiting for them to go up unless you plan on playing the game for the next 10 years +
They will bounce between 25-75k indefinitely. Of course the only thing that will alter the prices dramatically is if JaGeX decides to finallyyyyyyyyyy stop releasing them into the game.