agreed, this is scummy. thrift and secondhand stores exist to serve a certain underprivileged segment of the population. not to facilitate arbitrage. but to each their own.
I’m on the fence about whether this is scummy. On the one hand, it is diminishing an institution that families like my own relied on to have halfway-decent things for our home. On the other, thrift stores could sell these things themselves and have more revenue to support charitable causes if that’s what they should be doing. I don’t think GP is a scum bag, but when a VC backed iPhone app shows up to gig-economize mass thrift store raiding and selling online I’ll be bothered.
That said, I don’t think “we shouldn’t let everybody shop there then” is meaningful. Means testing is itself expensive and would likely penalize the very people who need thrift stores. Some things depend on the members of a society having a shared sense of what is and isn’t decent. Halloween candy is free but if I organize gangs of kids to empty out every candy bowl and sell it online, Halloween won’t be any fun.