I live in NorthWest Indiana, so no matter how many miles I set my distance to, I still get shops in and around Chicago.
Most company's schedulers have never driven the Kennedy, Edens, the Stevenson, the TriState nor the Dan Ryan (if you don't know what these highways are, you're not from Chicago). They use Google Maps to determine how much distance each shop is worth, almost never factoring for rush hour traffic or accidents, which are a daily occurrence here. It's our jobs as independent contractors (and ultimately, as humans) to know our own worth and what each shop is worth.
The first advice I always give when people ask about becoming a mystery shopper is: 1. Setup an email address specifically for mystery shopping. I currently have 9777 unread emails. Why? Because I browse the daily emails multiple times a day and skip over the schedulers and companies that don't value my time. Why not unsubscribe from their email list? Because companies eventually get new clients and/or bounce around new shops, or, as one company has recently done, the company learned that, if they want their $7.50 shops to be completed before deadline, they might want to add a "Submit Offer" button.
I make over $600/month on shops and have decent relationships with many schedulers.