It is *usually* a flat fee plus the extra fee for Greek, but as with everything YMMV.

Generally speaking, if a provider advertises on her site that a certain extra trip is $, does she mean per hour or per session if you are scheduling multiple hours?

Most escorts advertise a flat fee, meaning nothing extra.  You should be able to locate her hourly fee very easily on her web site. You should also be able to find reviews of her here or other national review boards. If this is not the case, simply move on.

and if not, then I'll pose it because I've often wondered about it.

Say a provider has a rate of $$$/hr, with $ extra for a trip to greece.

Now say you want to see her for two hours (Assume that her 2nd hour rate is the same as the first though it is often lower.)  

Now, does the paying of $ for the trip to greece entitle you to two trips to greece, or would that be $$?

It probably varies by the provider, but I wonder what other's experience has been.

Also, if you see a provider for an overnight, is the trip to greece tossed in as a bonus for booking so much time?

I didn't make my post clear after reading it over. I was trying to answer that question but didn't make it clear.

Usually if she charges $500 for two hours and $100 for Greek and you book two hours it $600 totaly fee. But YMMV as each woman sets her own rate, but that is how it is usually done.

I want a trip to greece.  The provider lists her fees $250 per hour  $100 extra for trip to greece.  $450 for 2 hours.  $600 for 3 hours.  I want to know if the $100 extra is for each hour or covers the entire length of the session  ie.....  3 hours plus the greecian vacation would be $700??

It seems like over the course of 3 hours, some time in France and other realms would take up most of your itinerary.

Of course there would be trips to other destinations.  France, Russia, Italy....