You have two things at work here, speed of content delivery and speed of development, and you have to decide which is more important. 99.9% (don't you love made up statistics) of the time, speed of development is primary, because the speed cost on the content delivery is minimal.
Where you go another route is when the site you are working on is incredibly high traffic, IE an Amazon or a Buy.com, but it is important to note that both those examples use the DB backend, they just throw some serious hardware at the problem until the speed is acceptable.
The expense (in time) of the database queries depends on how well those queries are formed, how big the tables are, the hardware hosting the database server, and so on. Usually, for small e-com sites, it isn't anywhere near high enough to justify the massive amounts of extra development time involved in creating flat html.
Of course, you could go the really sexy route and have some sort of content editor that used the database backend to create the product pages, but it might also not be worth the effort.
The long and the short of it is, in your shoes, I would go for the database backend in a heartbeat.
tD
