You can't gauge the complexity of the site soley on the number of people. I've seen places with as many as 3 people for 100 users and other sites with 5 people for 500. It depends on the complexity of the environment. 500 cookie cutter call center desktops locked down to about 3 menu items can be maintained by a few good engineers whereas it would take an army to maintain 500 desktops with all different configs and no standards.
Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE