Is it me or has anyone noticed that auction price values on retro video games for any system has gone up in the last 3 yrs?

Snatcher fetched anywhere from $100 to 150 three years ago. Now it is $200-250.

A lot of SNES completely boxed games havegone up $50.

Super Metroid used to be around $50. Now averages around $90-100

Wonder why that is. Your thoughts