The professional pet sitters around her charge a minimum of $20/visit, or $35 for 2 visits/day.
I pay the neighbor kid about $20/5 days. I also try to remember to buy them something like a T shirt.
If a neighbor adult does it, I usually get a gift certificate to a local restaurant for about $20. I feel odd giving a neighbor money. The only reason an adult ever stops in to feed my dogs is one of my dogs bites and the mother doesn't like her 13 year old going in my house, whereas the 13 yr old doesn't mind, he knows how to avoid the dog.
All anyone ever does is stop in and feed them. Having someone come in and spend time with them costs more, but back to that biting thing, I don't ask for that.
When I drop my guys off at friends houses for extended trips, I buy dinner at a nice restaurant, my last 8 day trip cost me $140 dinner for the 3 different pet sitters. I have too many pets.