The most expensive comic I own currently is X-Men (1963) #101 First Phoenix. It’s in VF/NM and going up in value due to the X-Men/Phoenix movie coming out next year. Need to CGC it.
I have issues 94-200 plus some key issues in between up to issue 500. #94 is worth more in guide but it’s in G- condition.
DC book? Batman Damned #1 First Printing. Bat wang issue. LOL!! Both variants. Those books will sure go up in value over time.