The higher paid shop may have been a reshop that got thrown at the scheduler on an extremely hectic day when she didn't even have time to get through all her email. (Maybe the subject line in your second message led her to realize that it was very urgent?) There may have been other requirements on the $40 shop (maybe a particular employee had to be shopped ("targetted"
and there was a very small window during which that employee would be working alone or something along that line.
By withdrawing from the shop so late in the day, you probably ratcheted up that scheduler's stress level considerably. I do know that most schedulers resent being asked to up the pay on a shop after a shopper's accepted it and especially on the date the shop is due. It tends to make them feel their shop is being held hostage.
I'm not taking sides but only trying to point out that we don't always know what unknown factors are affecting something that seems clear-cut from our end.
I don't know if it's the same mattress shop but I've done several at the same location and they are time-consuming if the salesperson does their job. On the plus side, I've learned an awful lot about mattresses! And pillows. And mattress pads! There's a 6-month rotation on the shops I've done so that probably helps account for why they sit so long on the boards, too.
If you feel badly about unleashing on the scheduler, why not email her and tell her so. There's no guarantee that it'll help your relationship with the MSC but there's a good chance it will be appreciated and at least you'll feel better about it. You may also learn the background on the two different shops on the same day for differing amounts.
Just mho, for what it's worth.