Has anyone ever attempted standby from a different co-terminal airport when using AAirpass? Before you say, "Why not just change the ticket?", there are a few routes where two airports within the same city will have a distance slightly more or slightly less. So if flying out of Airport A, you may have 1504 miles, when flying out of airport B, you may have 1495 miles. The 1504 mile flight will be significantly cheaper than the 1495 mile flight because the 1501+ multiplier drops. This can be a several hundred dollar difference in those cases.

If you did successfully standby at the other airport, were you billed based on the new (more expensive airport) or the original (less expensive airport).