Ha! Ha! I've bought THOUSANDS of '60s Soul records for 10¢ (US) each or 5¢ each, at record shop bargain bins, Woolworths' 10¢ sales and in thrift and junk shops, all within 1-3 years of their release. I would be dead before finishing the list on this thread (I'm 66 years old, and I'm a slow typist). And, yes, many (if not most) would now be considered "Northern Soul" (at least one side).
My best find was NOT NS, however.
In 1966, i was in a usually heavily picked through "Goodwill Store" in Los Angeles, and for some reason (instinct), I moved a bookshelf (which had only a few old children's records on it) , just for a quick peak behind, as I was frustrated in finding NO records to look through. Lo and behold! There were 3 45 RPM records that had fallen behind the shelf. One was "Dreams of You" by The Royals on Okeh Records. A Black R&B vocal group harmony record from 1952 (worth over $1,000 US at that time, as well as a 45 by The Aladdins on Aladdin Records from 1953 (worth about $300 then), and a 45 by The Five Keys on Aladdin from 1952 worth about $500 then. The Royals was in M- and the Aladdins were in VG++ condition. That was the highlight of my thrift-shopping career. When I told Steve Propes about that find, his face turned all sorts of red and purple. That made me feel better about all the records that were held for him to look at AFTER I had visited many thrift shops, because propes had bribed those workers with gifts of pies from his pie delivery route (he drove a truck delivering pies to groceries and restaurants).