This topic comes up from time to time. The older threads were closed so I have to make a new one.
Basically, one of the concerns I see in doing these shops is most multi-location retailers are tracking people who do returns. The newer method is to centralize these across retailers. This is definitely a reason for me to not do returns if my own returns in the future would be impacted. I think we have all see return policies be reduced or impacted because of abuses in returns (clothing or other industries).
Sometimes the shop fee is okay for these shops, but sometimes they are not. If a retailer doesn't want to talk the cost of the item, then they should just do the shop as a window shopping style. Obviously, there is a shopper for every type of shop, but I find it interesting that people accept these shops when tracking the return is common (whether by requiring showing ID or refunds back to a card - those names on the card are being stored somewhere).
I recently did a shop that usually is purchase/return, but because the specific location type doesn't take returns, there had to be a small reimbursement allowed for the purchase. Okay with me. Of course, if my shop got rejected, it would not be good.