It must design the Style Guide, User Guide, Help system and Writing HTML Tutorial for the users, the tree hierarchy and administrative issues. That is the 'secret' of the higher costs for a commercial site. A big corporation or academic site will become stabilized in eight to twelve months after its initial setup. That depends on many things. Note that this system price is for an entry point level, a RISC-based CPU with 16 Mb RAM and a 500 Mb hard disk.
Web wizard to smooth the things.
Additional engines commercially available provide video and music playing in real time, fuzzy database search, automatic forms processing, secure commercial transactions, client authentification, etc. In any case select a supplier that can build a machine mixing and matching parts, because some hardware combinations are deadly. That depends on the complexity of the whole system. Also you can consider 3D block renderings of your installations, but it will cost more. Travel expenses, accomodations and meals are extras.