I'm not sure anyone who shops regularly at a thrift store could be said to care overly much about labels.
We shop regularly at thrift stores and yard sales (more of the latter nowadays, they have better deals) and we look exclusively for labels, not so much for snob appeal but because they tend to be made better. We also live in an area that has massive amounts of yard sales 10 months out of the year. We go every Friday and Saturday, some Sundays and off days for moving sales. During peak yard sale season it's not unusual to go to over 100 homes in a day. We've never seen a high-end bag for 95% off.
Keep in mind that we don't consider Coach or D&B to be high end, we're talking LV, Prada, Hermes, Gucci, etc. Plenty of fakes, never the real deal.
Clothing, you can find. Leather goods would be like hitting the lottery. Not only do you have to find someone crazy enough to put it out you would have to be one of the first people to arrive, because it would be snapped up in seconds.
You would have an even smaller chance of finding a deal like that at a thrift store than a yard sale. The donor would want a tax receipt so they would know its value. If they didn't an employee would either put it aside where they keep the more valuable items or save it for a relative.