After a system has been released it starts to build a backlog of people who want to buy the system but are only willing to pay a certain price which is less than the current selling price; these people are not willing to wait around forever and may move on or decide down the road that it is not worth the price they were previously willing to pay.
When a system gets a price cut the people who were in the backlog of potential purchases become highly motivated to buy the system and there is typically a massive sales spike that lasts a short period of time (usually less than a month); after that spike sales return to a lower rate more representative of the average demand for the system.
A reduction in sales should be expected, it is not a bad sign.
