Paid and Partial Paid bids DO NOT cover alternates, additional coaches, or substitutes brought in case of emergency. This means they are not on the roster prior to the worlds event. They will only pay for alternates and substitutes that are turned in on the official roster prior to the worlds event. (I think) lol
Your bid DOES cover substitutions that your properly identify on your roster by the deadline. This can get a bit confusing based on what is posted so far so here are some scenarios I have seen:
Scenario A: Susie Fierce the base gets hurt bench pressing a football player. It happens before the roster is turned in so the coach substitutes her with one of the team's allowed subsitutes. This should not decrease the amount of bid money based on the number of athletes who competed when they earned their bid.
Scenario B: Susie gets hurt after the roster is submitted (anytime after the roster is submitted including at Worlds) but the coach submitted 7 substitutes and 3 alternates. There should be no decrease in bid money, but the gym is responsible for any changes to travel costs, accommodations, etc.
Scenario C: Susie gets hurt but the roster was submitted with a max of 10 substitutions already. An alternate can be added still, with the gym paying for the travel costs but the team can't have any more substitutions, so they will have to compete minus one athlete leaving her spot open or replacing Susie with the new alternate and removing one of the rostered substitutions so that there are no more than the 10 total max.
Last but not least you can't add a third coach on the roster as one of your substituions and get bid money for that coach.
I know this can't possible cover all scenarios, but hopefully helps make sense of the rules with some situations I have seen or heard of.