Before I sold mine, I had no idea what they were worth, although they were mint. I'm not trying to state that their actual aftermarket value is ~$75/pair, but doesn't $15 (or even $25) seem darn cheap? Roger, you basically got them for free (sans shipping - assuming they came from the USA).
I guess what I'm getting at is....I have no idea the value of the 300 bodies, but $75 seemed like a decent sale price (to the buyer and myself) considering my initial investment in the pair as full mics.