Soul is the hot market right now. Some of the real obscurities are bringing insane amounts of money.
I know, many of the records I picked up on record buying trips, for 5 cents sold for hundreds of dollars on Ebay. Back in the old days the black music was not played on the major white stations, that's probably why they became obscure. If you wanted to listen to them they were on the very end of the AM band. Being from the NJ/NY area, we had a nice selection of stations.