Since I'm broke, I was going to go through my parent's LP and tape collection today. My local thrift stores have no shortage of LPs, either, so I've always meant to take a gander at completeds. From clicking through pages of them, I take from it that unless it's a sealed Beatles or Zeppelin, or unless it's "first press" of some obscure 80's punk band with a crazy cover, you better check it out on an eBay app before you buy it.
But cassettes are what blew my mind. Look at this. And this. And this. Don't forget to click here.
I mean, let's be honest here, if you were glancing through tapes at a yard sale or thrift store (and do we very often? No.), would you pick up one from some obscure rapper from the early '90's? Or an old Wu Tang tape? Heck no. But now you know!
I'm pretty sure my parents don't have any unknown rapper demo tapes. And all of my old ones are likely to be Ace of Base singles, not Eminem. Dang!