10 eth? Good luck with that, however you have an anon account in opensea, there's no link to your other art to even start to valuate your work. Right now you are outsider art and while that has market, it has way more artists too.

3 days isn't unusual for painting to be finished. But it would be unusual to pay for 10k per day to unknown painter.
I know a lot of painters / artists that are using weeks or months to finish their paintings.