Amazon's Strange Pricing

I buy from Amazon, as it is easy to search for stuff, keep it in a wish list or shopping basket and buy when you are ready. I don't understand, however, the weird price cycles that some things in the shopping basket go through.

A few days ago I got this message:

Please note that the price of The Wild Geese (30th Anniversary Edition has decreased from $17.99 to $14.99 since you placed it in your Shopping Cart. Items in your cart will always reflect the most recent price displayed on their product detail pages.

Now I get this message:

Please note that the price of The Wild Geese (30th Anniversary Edition) has increased from $14.99 to $17.99 since you placed it in your Shopping Cart. Items in your cart will always reflect the most recent price displayed on their product detail pages.

Did I miss a run on the film? Has the supply gone down dramatically? Has the need for DVD discs gone up dramatically that they are grinding up recorded ones for fuel use or something?