The price of a Chicago Board Options Exchange membership retreated from the one-year high of $2.8 million paid two weeks ago.

One seat sold today for $2.63 million, or 6.3 percent less than the Oct. 19 transaction, according to CBOE's Web site. A second fetched $2.78 million.

The $2.8 million paid last month was more than double the three-year low of $1.2 million in March and 17 percent higher than the prior sale on Sept. 22. It followed a Crain's Chicago Business report the day before that CME Group Inc., the world's largest futures market, is "putting out feelers" to acquire CBOE for about $5 billion. Crain's cited people familiar with the discussions.

The appreciation echoes the New York Stock Exchange, the last major U.S. market that switched from member ownership to for-profit status. The value of NYSE seats jumped 66 percent in the three months before the company announced it would buy Archipelago Holdings Inc. in April 2005 and become publicly traded. CBOE also plans to demutualize.