In a further sign of the housing market's revival, the median price of existing single-family Bay Area homes in December jumped nearly 24 percent from a year ago on modestly improved sales, according to a report Wednesday.

But some experts cautioned that the trend isn't evident everywhere.

"There is a big shift going on regionally," said Andrew LePage of the real estate information service DataQuick, which issued the report. While sales of relatively inexpensive homes have been limited, because such houses are in short supply, "the mid-to-high end is picking up and getting back to a more normal level of activity."

This Tuesday, Aug. 21, 2012, photo, shows an exterior view of a home sold in Palo Alto, Calif.   (AP Photo/Paul Sakuma)
This Tuesday, Aug. 21, 2012, photo, shows an exterior view of a home sold in Palo Alto, Calif. (AP Photo/Paul Sakuma) (Paul Sakuma)

The median price paid in the nine-county Bay Area hit $470,000, up from $380,000 in December 2011. The last time it rose at a faster rate was in May 2010, when it increased nearly 29 percent, LePage said, adding that the median price in December was the highest it has been for any month since July 2008, when it was $485,000.

The median price rose about 22 percent to $650,000 in San Mateo County, 21 percent to $602,500 in Santa Clara County, 23 percent to $449,000 in Alameda County and 29 percent to $330,000 in Contra Costa County.

The most the Bay Area's median price has ever been was in July 2007, when it hit $738,500. That was just before the housing market collapsed, plunging the price to a low of $295,000 in March 2009.

In the nine-county Bay Area, a total of 5,464 homes changed hands in December, up nearly 2 percent from the same month a year ago. Sales rose about 10 percent in Santa Clara County, 4 percent in San Mateo County and 3 percent in Alameda County, while dropping 2 percent in Contra Costa County.

Although demand remains strong for homes in every part of the Bay Area, LePage said, sales of low-priced homes have been hurt by limited inventory. That's partly because fewer of them are winding up in foreclosure. In addition, he said, "you still have quite a few people who are underwater" -- they owe more on the house than it is worth. "So they are stuck. They can't put their homes up for sale" without losing money on them, he said.

But sales of more expensive homes are picking up. With mortgage rates low, the economy on the mend and employment picking up in the Bay Area, "people are feeling more confident and they are more willing to buy a home," including ones in pricier areas, LePage said.

At the same time, many people who had deferred selling their expensive homes now seem more eager to put them on the market -- and are being rewarded for it -- said Richard Calhoun of Creekside Realty in San Jose.

"The market is superheated in some ways," he said. "If it's priced right and there is nothing wrong with the property, it's going to sell immediately with multiple offers."

Doreen Roberts, immediate past president of the Bay East Association of Realtors, has seen the same thing in Alameda County.

"Low inventory and high demand turn into multiple offers, often with properties being purchased with cash, well over the price being asked," she said, adding that many homes sell within a couple of days and buyers are especially eager to snap them up in the top school districts.

Contact Steve Johnson at 408-920-5043. Follow him at Twitter.com/steveatmercnews.