by Daniel Nissanoff (Penguin Press) 256 pages, $24.95

If you think putting out $700 for a stroller is foolish extravagance, think again, says Web entrepreneur Daniel Nissanoff in his new book Futureshop.

Nissanoff says buying such an expensive stroller makes perfect sense. He points out that celebrities such as Gwyneth Paltrow and Madonna pay as much as $2,800 for Silver Cross Balmoral strollers, an exclusive brand that has become a status symbol on Manhattan's Upper East Side.

But Nissanoff is not arguing that a middle-class family should pony up $700 for a stroller just to show off, when it could probably buy a serviceable plastic one for $12.99. Here's what he says:

''Buying a new stroller for $700 is a good deal. A liquid secondhand stroller market means that your child is safe and happy in a stroller that you're proud to push, and then, when the harness is too snug, you can sell it for about $550 on eBay. It will have cost you about the same as if you had bought a mediocre stroller to begin with. Even a black Silver Cross Balmoral goes for about $1,950 on eBay, saving one lucky parent hundreds of dollars,'' Nissanoff writes.

The stroller is only one of scores of examples the author provides to drive home the point that consumers today are increasingly shedding their ''accumulation'' culture mind-set and are moving toward an ''auction'' culture mind-set.

He means that consumers are buying more things with a plan to use and resell them while they still have value instead of keeping them until they can only be trashed or donated.

For the most part, eBay and some of its Web competitors are driving that trend, Nissanoff says.

But despite the success of eBay, which in less than a dozen years has evolved from a small experimental auction to an international behemoth, it has not nearly reached its potential.

EBay and most of the other auction sites are too difficult for most people to use. But the number of facilitators such as drop shops, where one takes items to be traded, is rapidly increasing, he says.

Futureshop reviews the history of the various forms the secondary market has taken from medieval times to the present as a platform for projecting its future. The book is a good read from that perspective, as well as for the practical advice it offers. It would be a good investment to buy it - new or used.