Regarding schedulers/bonuses; Paying a bonus from their personal finances is an option that some will take to assure their own bonus for filling a group of shops before a deadline. They are simply sharing their bonus with you, so I don't see how it would be unethical. If it's the last day of the quarter, the scheduler has one shop left and is looking at a $500 bonus if they get this very last shop in, you could probably negotiate a hefty bonus from them.
That said, I find end of the month/quarter bonusing to be a somewhat lazy approach to scheduling, which creates an expectation of those bonuses and a continuing cycle of begging for shops. Schedulers are, in essence, creating their own problem. I say this as someone who has been a scheduler, so I understand the issue pretty well.
At the beginning of any quarter/month, I already knew where my hard-to-fill locations would be. It would have been foolish of me to wait until the last minute and then beg shoppers and/or offer bonuses. That's when you get shoppers who know the system and are going to milk it for all it's worth. If I called a shopper on the 10th and offered them $25 to get to Podunk in the next 2 weeks, they would probably be easier to deal with then if I called on the 29th and asked what it would cost me to get them there the next day.
You also have to keep in mind that if your job is to schedule shops and you are low on shoppers, your job is also then to recruit shoppers. Too many schedulers rely on MSCs to supply a list of available shoppers and then just simply put names into shops. If a scheduler has to pay a large bonus for a particular location, they would by much smarter to then put some time/energy/money into signing up shoppers that live near the location....and not repeatedly beg the same shoppers to drive long distances for the shop.