I had exactly the same reaction and the same questions as just articulated by Ruralcarrier. Furthermore, although I don't think you meant it this way, the use of the terms "modest" and "budget" sounds a little condescending, like those renters don't deserve the same consideration as high-end renters. Just sayin'.
But this seems to boil down to what appears to be a classic case of two parties having unfulfilled expectations of reasonableness and/or understanding, and escalating the situation by refusing to engage the other party's point of contention (kind of like Republicans and Democrats in DC right now).
So if you handle millions of dollars of transactions each year, that means you earn hundreds of thousand of dollars in revenue each year. I see more upside in just reimbursing the $200 (with or without receipts - by the way, who ever asks for a receipt for a beach chair?) and being done with it. I don't see any upside in continuing the fight, just more negative press for SMRC.