What seems like an extreme parabolic rise on a linear chart looks like a more steady rise on a log chart, followed by consolidation (bull flag?) over the last couple years.
Now a warning, the data for the average sale price isn't perfect. In order to try to get the average baseline sale price we did a rough elimination of large sale prices, since these were throwing the averages out of whack. We'll probably go back over this and try to use a more refined standard deviation calculation. But the chart should work fairly well as a rough approximation of baseline prices for these domains over the last decade.
We'll post more log charts for other numeric domain categories in the future.