Former seat holders of the NYSE ( NYX) will see their dreams of riches come true next month when the newly public exchange lets them cash in their stock via a secondary offering. In light of that, nothing could be luckier for these expert market makers than the dizzying run the shares have taken over the last year. But while these capitalists await their payday, others struggle to explain the breathtaking ride the NYSE's shares have taken since making their debut last week. Some sense a sinister undercurrent, noting the issue's small float has made the stock hard to borrow while volatility has mushroomed -- two negatives for would-be bears. "The people who own the stock, the members, are very happy to keep the stock as high as possible to boost the secondary offering," said Junius Peake, finance professor at the University of Northern Colorado. "To me, the stock is unusually high." NYSE shares, which closed Friday at $85.75, have run up almost $18, or 27%, since being created through the merger with Archipelago on March 8. The float is indeed small: Only about 24 million shares are available to trade, just 16% of the total shares outstanding. The rest are controlled by seat holders, including many broker-dealers who are poised to sell out in the secondary. Still, the issue is averaging more than 1.5 million shares traded a day. Such a high volume and low float tend to cause volatility, a quality that is more than reflected in the prices option writers are demanding for NYX strikes. Investors bearish on exchange stocks see parallels in the current froth to the Internet era of the late 1990s. After hot IPOs are sold, merger buzz runs wild and optimistic growth projections fuel runs to heights that are hard to justify through fundamental analysis.