Very old Western Electric tube amps and mixers, RCA 77DX ribbon mics, Nagras. Who knows but old Audio Developments mixers could become collectible one day, so I can unload one. I invested in gold shares, so what do I know? ;-) it's a market, timing can be everything. Hard to predict what people will care about in the future. The nice thing about the old stuff is it's repairable, pour milk into your Macbook it's value will be zero. I'm still looking for Ampex suitcase speakers with 6v6 tube amps built in, but prices seem high. I have 160 10 inch reels of tape 1/2 track stereo with a music library on them, no interest on Kiijii, along with a mostly rebuilt Revox A77, no interest in it either. You might be better to buy property in Detroit. Buy low sell high, seems to me some old gear is too high.