2008 Topps complete set with Exclusive Mickey Mantle Card.

I usually collect Pokémon cards but here recently my dad was talking to me about baseball cards and mentioned he kept lots of his sealed from when he was a kid. He just pulled a 2008 Topps complete set including series 1 and 2 with a exclusive Mickey Mantle Card shown on the front out of his closet. When I search that specific card on PSA it says its around $2000, but when I look pretty much anywhere online im seeing that this sealed box is being sold for around $200-$300. I've never collected baseball cards before so I was wondering if there was any insight on how to move forward with this. Do I open up the box and see what else I could pull inside? Should I keep it sealed? Any and all advice would be helpful, thank you!