Brands will vary depending on the higher end stores within a certain proximity of any given thrift. One of my thrifts produces many Hickey and Oxxford suits. However, across town, I tend to find more Brooks Brothers, Samuelsohn, and Coppley. I don't thrift many suits these days. First, I rarely wear them. Second, if I am thrifting for profit, I tend to do better with shoes and ties. Suits require more preparation and headaches prior to listing.

 

It really depends on where you live. In the wealthy beltway community thrift stores nearer to DC, I sometimes find nice H. Freeman, HSM or Cricketeer suits that don't look dated.

Finding a good looking suit that also fits is the real challenge. For business suits, I have mainly relied on ebay. I have to go through hundreds and hundreds to find a decent 40R even there.

 

My area is a metroplex consisting of two cities and the surrounding areas. There is no lack of thrifts (at least 50 to 75) and you could not possibly hit them all in less than three or four full days.
I probably average 20 stores a week (most on my lunch hour or on the way home from work.) While you have to get out there, I do think that your area determines what you will find for the most part.
I see plenty of suits in the Dallas thrifts especially. 50% is probably Jos Bank and Mens Warehouse. Another 25% is lower level like Alfani and Perry Ellis. (You can make the determination if they are actually lower level.) Then more than a few Asian MTM (I do not yet consider myself qualified to judge the value of these.) The rest is a hodgpodge of clearly dated stuff along with some Gems. I dont see much Brooks Brothers here. What may seem odd is that I have probably thrifted more Oxxford than all of the other higher level brands combined (Canali maybe 3, Brioni just 1, HSM Gold Trumpeter 3, Samuelsohn 2, no RLPL, no Cuchinelli, no Kiton.) As Monocle has previously pointed out this is also not a great area for high level footwear. Fortunately for me, at a basic 42R many of these finds are close enough to fit me.
I can say that I see decent business suits (Jos Bank Signature Gold) in what seems to be good condition on a daily basis at a decent price (between $15 and $30 per suit. I generally try to hit the major goodwills in Dallas only on half price sale days which usually are about every other month.) As I dont wear suits to work and so far, have only sold my finds through a reseller, most of these stay on the racks.
I read somewhere that a good rule of thumb for thrifting and reselling is to only buy items which you think can sell for at least five times what you are paying. I think that is a little high and I will still buy a suit for $25 which I feel confident should resell for $75 but this is still very new for me. As Dr.L pointed out, I am also trying to develop my knowledge of ties as these are often 2 bucks or less and very light for shipping.
What I can tell you is that I have determined that online secondhand mens clothing is one of the best values you will find. This is even more true if you follow forums like these where you can get deals not open to the public and if you are knowledgable about brands like Samuelsohn which very few people know about but make very good quality suits.
If I was doing a strict value measurement, I have no doubt that buying online would beat out actual thrifting for me. There is just too much time, gas money and wear and tear on your car to make this worth it unless you really enjoy the hunt. But of course, I still really enjoy the hunt. When I saw that Brioni suit last week in a thrift I never expected to find anything other than maybe a older tie... Made my entire week!

Anytime, you want to take a thrifting trip to Dallas just drop me a line, would be happy to show you the places I go.

 

I've seen decent business suits at thrift stores from time to time, but I'm a 34 inseam and I have literally never seen a single suit with trousers that long. You're better off spending more money and less time on eBay where people like me sell whatever decent stuff they find thrifting that doesn't fit. No matter what you do, spend what you didn't on the suit at the tailor. An older, high-quality two-button suit with reasonable lapels can be made to look much more modern and less like you're wearing a used suit.

 

Anytime, you want to take a thrifting trip to Dallas just drop me a line, would be happy to show you the places I go.

I'll take you up on that offer one day.

 

Sounds great. I'd even offer to put you up but I have found that teenage daughters are like a gas, their stuff expands to fill any space.

 

I'll be working in Dallas for 10 weeks this summer. I'll definitely reach out to you then.