When I am doing routes, I figure the round trip mileage to each station from my home, divide that by 25 (my gas mileage on my car) to come up with how many gallons of gas (rounded up) it would take to drive there and back. I then multiply the number of gallons by the prevailing rate for a gallon of gas.
I used to just figure the total mileage for the complete route and add 10% to it for misdirections and then divide it by 25 and multiply it by the average cost of a gallon of gas. Then I would divide the amount by the number of stations to arrive at an average for each station and request that bonus for each station. If an overnight stay was required to complete the trip, I also added an additional $100 to cover the cost of the room.
However, most schedulers for my MSC ask you how far the location is from your home and use that as a basis for the amount they're willing to pay as a bonus. It's weird. The scheduler for one vendor almost never haggles with me and gives me the bonus I am requesting; while the scheduler for another vendor always haggles on the bonus being offered leading me to either reject the entire trip or make a second offer that hits some type of balance between my original offer and their counter-offer.
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One buzzard to another while circling high overhead (paraphrased), "Patience hell! I want to shop somewhere."