Ha, never even heard of Black Mercy. This issue started to trend upwards a few months back. I'm not sure why other than people say it's a great story written by Moore.
No, it didn't. It's relatively hard to find (considering it's a regular Superman comic from the 80s) and even harder to find cheap, and it has been that way for many years now. Even the big online shops rarely have copies available.
BTW, the Black Mercy isn't a character, it's a parasitic alien species that is something between a plant and an intelligent fungus.
While many people would agree that “few” means three or more, the actual dictionary definition of “few” is, “not many but more than one.” So, a "few" cannot be one, but it can be as low as two.
You can use my link and see that it was selling for $40 in Jan.
I pulled out the copy I had. Bought it last year for $2 from a dealer.