Even though it was a promo only release (for Detroit Mayor Coleman Young) - it doesn't seem to go for much money- I've never seen a
copy sell for over $200 USD.
I would think many of the early Tamla releases (Satintones, Nick and the Jaguars, Barrett Strong "Let's Rock" etc.) and the Supremes
"I Want A Guy" on Motown #1008, and the Miracles "Bad Girl" on Motown G1/G2 would be much rarer.