Jim - I used to work the gates for SWA. If there was an unlimited jumpseat agreement with an airline, then of course those individuals went for free. For airlines that did not have unlimited jumpseats, we were allowed to put on two pilots from other carriers. If a third pilot walked up from another airline that did not have unlimited, I either had to refuse them the jumpseat OR suggest they go to the customer service counter to buy a non-rev ticket. So, it is not charging for the jumpseat - just following the reciprocal agreements.
Interestingly enough, I had the above scenario with the three pilots without unlimited jumpseats. I asked the Captain to sign one more jumpseat, and he immediately agreed to the request. However, I was working with a new gate agent, and she ran and told the supervisor. So, I got reamed about trying to help a jumpseater get to their destination.
Here is the funny part. The supervisor told me that we could not allow the third jumpseater because it was a violation of security!

I was on probation at the time, so I could not correct her!