Labels, labels, labels.
Once you have been thrifting for a while you will start to notice that certain brands appear almost infinitely and others are more elusive and therefore so much more of a thrill when you find them. The layers within that will be the condition of the item, as I have witnessed the tragedy many times of an extremely expensive luxury product worn beyond repair that has been left to languish at the thrift. The thing with higher end pieces is that, depending on the brand, they may or may not be priced accordingly.
It's common practice for some thrift shops to price certain labels and brands higher than others. As a buyer, this can seem a little haphazard and random at first, then once you have more experience thrifting you will come to expect pricing as typical for that chain. Typically each category of products will have a price range, for example 'women's jeans' range from $4.99-$14.99 at one of my usual shops with an average price of $7.99. I only search for mid to high end labels, and depending if it is a 'recognized' label by the shop I may see a product way overpriced, or under priced.
I tend to see American Eagle Outfitters jeans priced on the high end of the scale, but I have found designer denim brands priced at $4.99! Very well known 'mid/upscale' labels such as Michael Michael Kors, Lululemon athletica, and the label Wilfred from the Canadian retailer Aritzia are consistently overpriced at the thrift. When you find them for a good price it's usually because they have 'missed' a logo (common with Lululemon products since tags are meant to be torn out and logos can sometimes be in an unexpected spot like the bottom left lower back of a sweater).
The other reason why they may not be marked-up would be if they are in terrible condition (but beware, sometimes they will be marked-up regardless and it's up to you to be the discerning shopper and question the item's value given it's state!). Either way, the sweet spot is really the many high-end brands that are not as widely known, for example anything from Anthropologie. They carry hundreds of labels that are relatively under-known unless you are a regular shopper there. If you are relatively unaware of labels, thrifting is a great opportunity to hone your product quality skills and build your brand knowledge.
It's a great thrill to pick something out of the racks and do a quick google search on the brand only to discover it cost a small fortune at retail, and the confirmation that your ability to separate high quality clothing and accessories from the rest is not dependent on a recognizable label! Style plays a huge factor too. I will laugh out loud in the aisle sometimes when I see a ratty threadbare sweater hanging by one of it's many snags on a hanger and recognize it as a highly coveted boho piece by a brand like Free People, Wildfox, or One Teaspoon. You thought it was garbage and priced it at $2.99- and now it's mine: SCORE!
The first time I found a 'Rails' blouse on the racks, it was such a rush! I LOVE wearing button down shirts and the Rails pieces are the epitome of casual-cool...as far as button down shirts go. Retailing between $125-$175, they have always been at the top of my thrift list. It took me years, but I finally found one! A beautiful, light, white gauzy button down shirt with a slightly over-sized fit and a delicate window pane texture. WHITE is a colour that has difficulty surviving at the thrift, which made it all the more exciting that this piece was in perfect condition, and with a price tag of $4.49. **SIGH** it feels even better when I'd been crashing through the Old Navy shirts, all priced at $7.99 before falling upon this gem. This shirt goes with everything, for all occasions, in my opinion...but then I could be accused of being an 'overly casual' girl.
Authenticating a piece like this can be tricky, because it's easy to assume that since it is not a high-end luxury piece (e.g. Gucci, Chanel) that it would not be 'faked'. Sadly, it's shocking to see the range of brands that are faked and end up at the thrift. This is where your senses come into play! The feel of the fabric, the look of the stitching, the labels, loose threads (intentional, or not), comparable items online (what's off, was that shirt ever made in that colour), hardware (quality of the buttons). It helps if you have seen and held an authentic product in real life. It becomes second nature to your senses. I have tried on Rails shirts at boutiques, so I 'just know'. That gut factor comes into play all the time when thrifting- listen to it! Trust your instincts...and do your research. Happy thrifting!