Expensive Mega Man games

I know that some of the Mega Man games are really expensive. There may inevitably be no way around it. But I was curious to find out if any of you have had any good experiences finding old video game gems for cheap prices and where you found them?

I once got Crazy Climber for Atari 2600 for free along with 50 some other games. I don’t think they knew Crazy Climber was worth like $400.

Anyways I’m trying to get these games but they are super expensive!

MM 7

PSX (with case art and manual, these are expensive)
MM Legends
MM Legends 2

PS2 (with case art and manual, it is expensive)

(MM = Mega Man, of course)