A view from the inside:
I manage a large-volume privately-owned thrift store. On a daily basis, I deal with shoplifters, tag-pullers and tag-switchers. There is a perception that since merchandise is donated, that it shoud be practically given away. This fails to take into account all the costs associated with running a business - payroll, overhead, etc. The "donations" are purchased from charities. The items we sell are NOT pure profit.
That said, the members of this forum seem to be honest folk in general, so I'm sure most of you sympathize with business owners trying to cut back on losses. My policies in dealing with people who want their bargains even cheaper (or free) are: Missing tags - if the pricer for that dept. is here, I will reprice the item - tags do fall off by accident, but we do learn quickly who are trying to get lower prices; Switched tags - must be reprocessed the next day. 3 or more in your selections, you are ejected from the store - this is theft as much as shoplifting is; Caught shoplifting - police called, no exceptions.
My employees are taught to be polite and helpful - which is one reason why I resent people trying to rip us off even more.
A note on pricing - I have knowledge of better brands and teach my pricers accordingly. A Brioni shirt in LN condition at 15 bucks is still 95% off original price. That said, cheap stuff is priced accordingly as well and I don't put out damaged goods.
I love my business, I love my customers - the honest ones, and any business owner or manager should remember to treat everyone with respect and give as much benefit of the doubt as possible without letting one's business be compromised.