Hi Roger,
Judging by our Borneo experience, where many forum users were watching the PI website on a daily basis, there appears to be no rhyme nor reason to the pricing structure - prices for this May were high all last autumn until suddenly one day in October they dropped to a reasonable level for a day or two, then rose again! I think the safest way is just to keep an eye on their website daily until they drop - and then pounce!
Hope you have a great holiday wherever you are going!
Cheers,
Bob