It has been my experience with IPSOS that you shall see new shops initially on their Job Board at the going rate. You can select them and self-assign. These are not bonused, nor would they be (most of time anyway) - you can always ask the scheduler (more about that later).
As the weeks pass, they (IPSOS) add a small bonus amount if they are not taken. The experienced shopper knows their location and whether they are in a monthly rotation or a quarterly rotation and whether the bonus amount is acceptable.
With the monthlies, they are apt to be bonused much sooner and more often than the quarterlies for the obvious reasons. Monthlies need to be done before the month they were added ends while the quarterlies have 3 months to sit on the Job Board.
As for requesting a bonus from the scheduler: Typically, the scheduler is not involved during the "I Shop First" period. You can ask a scheduler for a bonus during that time, but I have found that they shall not do it, advising that they cannot, due to the "I Shop First" time period.
After that period ends, often you shall see a small bonus added to an unassigned shop. At that time, you often also see who the particular scheduler for the shop is in the shop description.
However, it has been my experience with IPSOS schedulers that when you do ask for a bonus amount, the scheduler shall want you to justify the amount, asking about the miles from your home, etc.
In my opinion, I feel I do not need to make a justification, but I'm assuming that they are tasked by the company to ask those questions. It is my own opinion that if they want the shop done and they have someone willing to do it, they should not be being asked about the absurdity of justification.
So, i have seen shops sit and sit and sit, well past their time to be reported. They are often not taken for many reasons. Distance, in my experience, is the most likely reason. There is nothing nearby to make a logical route. I once did a bonused Debrand and found there is no cell connection for miles. Imagine endeavoring to take your photos and then driving away to upload!
Anyway, there you have my feelings. Cheers!