The market for DSLR camera lenses is so vast. You can pretty much find a specialist lens for any type of photography whether it's from family photos, landscape photography all the way to professional product photography.
The purpose of product photography is to display an object as well as possible. You'd most likely be in a studio environment so there will be an available source of artificial source of light.
It's easy to get caught up in looking for the best 'f number'. I'll be the first to admit that. If you have the budget then by all means do splash out on a 24-70mm f/2.8 VR or a 105mm f/1.4 AF-S E ED but chances are you won't be reading this blog if you own one of these.
The most important question to ask is what are you looking to achieve? If the end result is going to be 1000 x 1000 resolution images for eBay then you're probably not going to need a top of the range DSLR with an amazing lens. You'd probably be better off looking for high quality lighting. However if you're looking to shoot a high end commercial brand that's going to be printed on billboards around the world, then you'll be needing as many pixels as possible probably in the form of a medium format camera.
At the end of the day, look for something that suits your needs rather than something that looks good on paper. Decide whether you need a prime lens or a zoom lens based on your photography practice. You might want a lens that covers multiple types of photography or if you only cover one type of photography, you would be able to look for a more specialist lens.