Prices have changed on most articles in my cart in between yesterday and today !

The title is self explanatory ! I built a cart yesterday with over 30 products, all from international warehouse. Today I wished to add an item and logged in again in a new window in case my cart disappeared !!! so I had yesterday's window with my items list, qty and prices. I re-built the same list and I realized that quite a few articles have increased in costs, not all but most of them, the increase isn't big at all, in the 1-5 cent per item.

I picked the same ones as I used the previous cart with items list to open a new window each time and add to cart... It isn't my mistake, the prices just change kind of overnight. Is it dues to exchange rates ? HK prices are by default in HK$ or US$ and I view them in Euros ?