In fact, I think that a very basic system for beginning could be developed quickly. As I said, my site was an enhancement of an older one, so we have spent about one month wondering how we could add the required bunch of features to the older site. (In fact, the resultant site was quite complex, featurefull...)
So, you should gain one month :)

You should gain more than one month since we had to learn the usage of CVS, XML::Parser and how to use Apache::Registry. More important, we had to find these tools. It's not obvious when you're just-a-newbie, and you don't know how-to-do and why =)

Nevertheless, it takes time. A lot of time, since there are always problems, and your boss/client always add some feature enhancement... (that's why it's important to have good written specs and a good contract, as it has been said in other posts)