From reading here, it seems there are two classes of shoppers. Just like there is fist class and coach in an airplane.
If you live in an area that is sparsely populated and there are a limited number of shoppers, you are in the front of the plane and in first class.
You can wait till the end of the month and look at the job rate soar as the the price of the shop will be driven up dramatically with high bonuses as the MSC must shop that one location in a city with no shopper that lives within 100 or more miles. Your a first class shopper and the MSC's will treat you accordingly. They need you more than you need them.
Then there is the coach section of the plane.
This is an area where there are plenty of shoppers. In the south where I live, the competition is even worse this time of year as the snow birds come down and are retired and have plenty of time on their hands and the density of shoppers is so thick that they know that they can get almost all the shops filled at the base pay. The only time they need to add more than $1-$2 to the shop is if it's in a bad neighborhood or in the tourist area where the shopper is most likely going to face bad service and need to write a longer report with more no answers. This is due to the burnout of the tourists that abuse the retail workers and the lifespan of an employee is that of a fruit fly.
The only time the bonus gets good is when there is a flake and they need it shopped that day or the next day and you get a phone call. Even then, if your too greedy and ask for more than an additional $10-$12, they will possibly reject your counter offer and go down the list and may not call you back. They have more shoppers than they need and know they can get the jobs done cheaply.
The same company may treat the first class shoppers completely different than they treat the shoppers in coach areas of the country. If your in first class, they can't afford to loose you. If your in coach, your as disposable as the luggage.