I've been 1st, 2nd 3rd even 4th camera on the job...
Person/studio w/ the contract gets the publicity regardless of how well the others one done. I had however, instances where clients have found me later on and used me directly, at which point a Standard 1st round commission of 10% I have given to the studio.
During film days, I delivered the film and got payed for the job. With digital, depending on the job, at the end of the day give the card to 1st shooter, get paid and leave. Now that my camera has 2 cards, I shoot on both and ONLY use the images to show of fellow photographers/studios (NOT CLIENTS) and even that with permission from the person/studio for whom I shot the job. But I shoot cards regardless of the job for safety concerns and when the job is loaded on computer & backed up, cards get cleaned.
Prices are simple:
I have prices that are for my clients and wholesale that are for times when I'm hired by someone else to shoot a job. Price w/ editing is higher then w/o editing - and its b/c it involves extra time.
hope that helps.
Good Luck