GPU and RAM supply doesn't change over the course of one weekend usually though. So there would have been no reason not to wait until Monday or do it before Saturday.
Based on the article it seems like the only information before the change was "some day in january we will change prices" which would not be enough for me as a customer...
Give customers time to react and plan, so announced at least a couple weeks ahead of time.
In many calendar applications one can actually configure things like that. Often the option is directly named something like "start week on Monday/Sunday".
We also shouldn't neglect the fact, that other cultures other customs. Maybe the week starts on Sunday in your location, maybe it doesn't in my location.