Trying to be helpful here, not critical.
Generally, cards with a crease (full on crease, not a "hairline crease") will grade as "Good", and "Good" cards from that era generally are worth 5-10% of the "book value". If it's a hairline crease, it could grade as "high" as VG, which then puts it in the 10-20% range. Asking 80% is generally reserved for Near Mint as even Ex-Mt only is 40-60%. Just trying to help you be more realistic in your expectations for selling a creased card.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 3/4/2024). I have added a large portion of my inventory to the site, and currently have trading turned on (details are in my profile).