Edit:
Re-reading the question, I think I should have just listed the different types of possible expenses rather than calculating the costs of different types of sites, so I'll try to do that now:
- Domain registration (annual)
- web hosting (monthly)
- unique IP + SSL add-on (monthly/annual)
- payment gateway (monthly + setup fee)
- merchant account (monthly + setup fee)
- design (one-off)
- development (one-off)
- usability testing (one-off)
- SEM or PPC advertising (monthly)
- one-off SEM costs like directory listing
- analytics (monthly)
For businesses, there may be other expenses like e-mail marketing services, online PR platforms, competitive analysis tools/services, and auxiliary marketing research services.