There is a fairly thin line between what makes working with a company a reasonable business proposition or not. Few of the jobs offered could be said to "pay well"--they just pay well when compared to other shops. Few companies "pay quickly"--they just pay sooner than other similar companies.
It really, for me, comes down to what companies are reasonable to try to deal with. I had a company I liked working with the schedulers. Last year a little $15 job I didn't receive a check for. They indicated they had sent it and quoted check number and date. That doesn't help if it never got to me. After several requests that the check be stopped and reissued, the company let the check go to it's last validity date and on a subsequent email told me they were "taking care of it today". No check ever arrived. We had verified my mailing address and indeed a checks for previous and subsequent jobs arrived without issue. Something like a dozen emails just to try to get paid. I have scratched them off my list of companies worth working with.
Another company others love. Their fees are mediocre. They then have way too many shopper contacts because of their inability to read. Their communication got worse, their website was slow and seriously extended the time to put in a report and when their scheduling became inflexible, that was it for me.
It is a fragile trust between shopper and company at best. I find that when a company persistently posts shops that are systematically too low fee to be feasible even if you are at the location already, there is little reason to trust them as a business partner. Sure, I will on occasion take a CoRI job with a substantial enough bonus that it is a fair business proposition, but those are few and far between. This IS a business, I AM a professional shopper and if all they or their clients care about is that a warm body appear at the shop site, that is their business choice. I am more disturbed that they then penalize warm bodies for not doing it right.