Well, please be assured that I am not, in any way, trying to raise anyone's ire. This is MHO only. I think that the "practice" of charging visitors who are joining a paid in full on site customer (for a couple of hours or the entire day) is absolutely reprehensible and is simply another example of "in your face" screwing of the consumer. The rationale of having to cover insurance costs for future liabilities or extra use of facilities is absolutely ridiculous. The insurer does not cost out the policy based on the number of paid guests or visitors or any other such number of random circumstances. The policy is based on industry standards, previous claims, etc. etc. I concur that the "base rate" does indeed take into consideration all of the costs for insurance, guests, visitors and so on. Yup, classic grubbing for extra dollars - kinda like having to pay extra $$$ to have a new propane tank purged, having to pay for air and water at your local "service station" and so on.
As always, YMMV
Cheers, all!
Mike