To update an existing list price on an artwork:
Go on the artworks's detail page and click "set price", set your new price, and confirm the transaction
To remove a list price from an artwork
The simplest way to do it is to click on the three dots menu on your artwork's card. Cards can be find in your collections or creations. Then click "remove list price".
Here is another, slightly more technical way to do it:
Check the URL of the artwork to see if it’s V1 or v2 token. For example, this URL is a V2 token: https://superrare.co/artwork-v2/the-scarlet-soldier-14872 For v1 tokens, you'll see
/artwork-v2/in the URL.
For v2 tokens just set list price to $0 and the price will be removed.
For v1 tokens, you have to send the token to a different wallet in order to clear the list price (of course you can send it right back again if you'd like!).
Note that it may take time for actions to be processed on the Ethereum blockchain.