@synapse, the amount I quoted is actually a little low. $250,000 is roughly the amount the company who hired us to build the site has paid us in consulting fees. Both companies have incurred other costs over the course of the project, but I would say the total cost is no more than twice what I quoted, and possibly significantly less than twice what I quoted.
We have developed the application ourselves (a team of 7 developers design and customer acceptance testing coming from our client) using open source technologies (basically the LAMP stack the Symfony framework) and a (mostly) agile development methodology. It makes pretty slick use of AJAX (most of which I wrote, building on Prototype and Animator). We also had the advantage of having a fairly mature backend system with which to integrate the customer’s frontend.
I completely agree with you that it takes real money to build a real website. The Pottery Barn site is such a site and to emulate it in any substantial way would cost a significant investment. The other figures people have proposed here ($70—$15,000) are just not realistic for anything approaching the quality and sophistication of the Pottery Barn site. Yes, you can get an “online store” up and running on the cheap, and it may be the perfect solution for your business, but it’s not going to be Potterybarn.com