Interesting!

Some people get a kick out of doing some huge number of shops. It is its own reward simply to live through that. Adding shops on the fly is fun, too. Usually, there is no time to consult a calculator or tax expert because you have to get the shop, get ready, and get it done quickly.
Kudos to the OP for doing forty shops in one day!!!!! I could not do that. Ever. I work every day in town at one or more jobs, so I only complete a few assignments per day on the few days that I shop. I am pushing for an upcoming two-assignment day. If a scheduler agrees, that will be a biggie for me. If it does not happen, I will have even more time for a fave store which must be combined with one or more shops. (This is how I justify going to that fave place which is not shopped.) Five, or maybe six, assignments in one day will just grind me down to the nub. I have done that and lived through it. One day, I profited close to $200 as the day progressed and I added bonused shops on the fly. It was fun, stressful, and big ol' kick in the butt all at once. My takeaway? If necessary, I could make enough money with little, big, simplistic, complex. low-fee, reimbursement-only, and/or bonused shops. I would not want to do it. I just know that I could. Knowing that is priceless. Thanks, OP!
Bach is not noise, Madam. (Robert, in Two's Company)