The Hamptons real-estate market is far more than beach-front mansions for billionaires.

An uptick in deals for lower-priced homes along the storied South Fork of Long Island—mostly by bargain hunting second-home buyers—has pushed up the number of sales there to their highest point since 2005.

Even on the island's North Fork, a quieter and more-affordable alternative that is a short drive from the Hamptons, buyers have stepped up activity, and prices have been rising.

The second quarter is the peak selling season on the east end of Long Island, and new market reports celebrate homes priced below $1 million that are moving quickly.

"You don't have to be a millionaire to buy a second home on the East End," said Dottie Herman, president of Douglas Elliman, a real-estate firm.

While prices on the most expensive headline-generating homes have risen to record levels, brokers say, lower-priced houses are still more affordable than they were during the last real-estate boom.

A report by Douglas Elliman released on Thursday noted 700 sales during the second quarter—3.7% above the same quarter in 2013. It is the most sales since the second quarter of 2005, when 786 homes traded.

Jonathan Miller, an appraiser and president of Miller Samuel Inc., attributed a rise in sales to "an expansion of entry-level homes, defining entry level as prices below $1 million."

During the second quarter, Mr. Miller said, the number of below-$1 million sales rose 6.6% compared with the year-earlier quarter and were the highest since he began tracking such sales in 2011.

Roger Blaugh, a Corcoran Group broker who is handling the sale of a contemporary house on a canal in East Quogue listed for $999,500, said many properties were priced below $1 million, and some for far less.

He recently helped a buyer, a year-round resident, snag a 1960s ranch house on two-thirds of an acre near Southampton Village. The house was listed at $539,000. "Affordability plays a big factor in the market overall," he said, "even though all the talk seems to be about the mansions and the $30 million price tag."

The median price in the Hamptons, $908,500, remained 17% below the peak prices during the boom, according to the Elliman report. It was also just below the $910,000 median price for a Manhattan apartment during the same quarter.

As sales of lower-priced home rose, the median Hamptons sale price was down 1.3%.

On the North Fork, the median home price of a home was just over half that of a Hamptons home—$477,500—and remained 21% below the 2008 peak. Nevertheless, it up 3.9% from the same quarter a year earlier.

An approximately 4,000-square-foot, four bedroom home is listed with Corcoran Real Estate Group for $999,000. Corcoran Real Estate Group

Ernest Cervi, a Corcoran managing director who is based in Bridgehampton, said that Corcoran data showed a significant increase in sales in the North Fork in the second quarter, as new buyers, first-time or second-time home buyers move into the market.

He said interest rates remained attractive, economic indicators were positive and some buyers worried prices might begin to rise.

Traditionally, the North Fork and Hamptons markets have been separate. In part, that reflected the areas' contrasts: the ocean-splashed Hamptons, summertime playground to celebrities and old-money families, versus the North Fork, a more sedate and modest string of communities, many with vineyards, bounded by Long Island Sound and Peconic Bay.

But as prices in the Hamptons rose sharply during the boom, many buyers were priced out. Meanwhile, the North Fork became more appealing with added amenities, from restaurants to high-end retailing.

To be sure, many lower-priced homes need renovation and not all neighborhoods have been seeing a sales surge. Thomas Uhlinger, a Douglas Elliman broker based in Mattituck, has a three-bedroom home in Cutchogue on the North Fork, with a dock on a creek, listed for $895,000 that has been on the market for many months.

He said buyers were looking "but not taking a swing," since inventory was plentiful and rising. But he said many buyers were realizing the North Fork was undervalued.

In recent years, he said most summer buyers came from Manhattan, but now there was a new trend, as younger, successful buyers in their 30s are looking over the East End: "A lot from Brooklyn are coming in," he said.

Write to Josh Barbanel at