I’m going to be a bit blunt, but unfortunately you didn’t score big in a cash sense. The tag on the arm is to make it easier to check brand on a store rack and is designed to be easily cut off–having it still on does increase its value as it’s a sign of low/no use. However, tailored clothing like suits and blazers are a relatively niche and very saturated market, so unless it’s a new or like-new 100% wool or wool/silk blend in the classic 2-button style and from a very well known brand (Brooks Brothers, Hugo Boss, etc.), it’s going to be very hard to sell it for much because people can just do what you did and go to a thrift store and choose from tons of suits for ~$8 each. Even if the store originally charged $800 for it, as another poster commented these suits are selling for ~$30-$100 on Poshmark and most of those listings have been up for months. If you’re very patient you could maybe get $20-$50.

However, if it fits well and you like it, you scored a fantastic clothing deal on a fun jacket, so congratulations! The money you saved instead of buying the $300 jacket at DXL is now free for your emergency fund!