I think that there are probably different service arrangements in place than the ones that we are typically used to dealing with in this area.  It sounds as if some people are providing services by way of simple service requests and without any formal contract in place.  While I've never opted to do this, as it sounds like liability waiting to happen, I can see how some services will do so for a per-item charge.  I prefer having formal contracts established with regular, ongoing clients that provide for flat monthly rates for recordings or filings. 

  I don't nickle and dime them with added charges for each filing.  I will present papers a couple of times each day and route things to them to and fro a couple of times a day on their own courier accounts.  The cost is theirs and they already pay me for having a daily route that includes them, so I have no added overhead for any back-and-forth. 

  It sounds like the business model of others is more akin to being a messenger service.  In which case, operating under such a model, I would certainly charge a per-delivery fee regardless of whether a particular paper got filed the first time or on the third attempt.  It would obviously be up to the client to fix errors and pay the delivery costs in and out of your service.