Do these portfolios also show prices? I've never seen such a thing (well, aside from off-the-rack TemplatesAreUs.com sort of sites).
If pricing is such a case-by-case matter then perhaps there should be something on the site that explains this.
I've dealt with a number of potential clients for Web development who came in assuming that site building was much like (in their mind) getting a house built. Two bedrooms, 2.5 baths? This much. Three bedrooms? That much.
I've had to explain to people that even getting a house built is not like that, that while there are some common aspects there are also quite a few things that are going to be unique.
Clients are usually well-meaning and earnest when they go shopping for a developer or a designer, but typically have no idea how things work. A little time explaining things goes a long way.