Buyers are busy buying, in most price ranges....

Home sales are on the rise -- on almost every price range:
- 4% year-over-year increase in sales under $200K
- 26% year-over-year increase in $200K - $300K sales
- 26% year-over-year increase in $400K + sales
So, what is happening with the $300K - $400K home sales?
As shown above, they are down 18% year-over-year, though they are up 25% compared to where they were two years ago. Maybe it was a temporary boom of these buyers over the past year??
Theories welcome!