No big changes from the previous month, according to numbers prepared for the Business Journal by HomeData Corp. and released this afternoon (subscription only). The median price of an existing L.A. County home in August was $550,000, unchanged from July and up 5.8 percent from a year earlier. Year-over-year sales took a 32 percent tumble, though the comparisons with the summer of 2005 are tricky because sales a year ago were still quite strong. This is the first of several housing reports for the month of August, and while the numbers deviate according to methodology, the trendlines are usually pretty consistent.