N-SB.org marketplace is a good place to look. Also monitor eBay, but from my experience, about 1/4-1/3 sold as authentic are fake.
There are prob. close to 200 sb dunks, and most go from about 80-300. Generally, the newer, the cheaper. Some of mine are 7-8 yo now, amazing to think they were on a shelf somewhere for 4-5 years before I bought em.