I've used a consignment store and my experience was great. I dropped off 15 pairs at RIF LA and 13 pairs sold within two weeks. The other 2, I took back and moved myself.
I'm 28 years old, and work 50+ hours a week. I'm been into kicks since the 11s in the 4th grade, and been selling for over a decade online. I used to sell on NT, and took the bus down to the USPS to ship them in high school before I drove. Consignment stores, especially established ones, have something online selling would never have...visibility and networking. I saw tourists who spoke no English came in the store and just point to the shoe and say the size. There's also sports stars and those with deeper pocket coming through to cop stuff. This is why the establishes ones are so heavy on IG and social media.
The sneaker culture now belongs to the kids, which means you have to deal with a lot of BS since kids are mostly broke. If you try to flip on eBay, you also risk the buyer not paying or trying to reverse the charge on you on some BS like 'he sold me fakes'. You also risk getting stuck up on CL, depending on your area and all that. On NT...it can take a while, and there's a lot of lowballers and flakes out there too.
Personally, I am happy with them taking the 15% cut and dealing with the headache. If they don't sell in 2 weeks, that's when I start listing on CL, eBay, etc. to increase my potential of selling.