Miller Samuel Inc. and brokerage Douglas Elliman Real Estate's second quarter report shows single-family home purchases topped a median of $2.5 million and exceeded the previous record from the first quarterly by 2%. Nearly half (45%) of sales in one of America's wealthiest zip codes were locked in a fierce bidding war. Buyers paid on average 7.54% over the list for homes in the last quarter.

The report provides evidence that a slowdown for Greenwich real estate is underway, and a turning point could be imminent.

"Greenwich is returning to Earth," said Jonathan Miller, president of Miller Samuel. "The intensity is not what it was."

Pruner, a broker with Compass Inc., wrote in a recent blog post about Greenwich, "it's not the market that we had in March ... there is a fair amount of uncertainty, and most buyers need a reason to move when such uncertainty is present. Smart buyers see this as an opportunity."