If you are unknown then you should price it by size.
These should be considered minimum prices for your efforts for paintings in acrylics or oils. These are wholesale prices and you are the wholesaler. Selling direct is wholesale pricing and people who don't know they are getting a bargain don't understand art.
A gallery will double or triple those prices for an unknown artist. If you are known there is no limit. Prices do not include frames.
Well known artists in Vancouver can expect about $5,000-$10,000 for a 36X48 painting. Collectible artists can expect $10,000-$20,000 for the same size, may only paint 10-20 paintings a year and usually sell out immediately.
You can always ask for an offer.
Often, with well known artists, people are buying a collectible commodity... they are buying a signature.
Many don't understand that a lot of art is valuable because of the history of the artist and hasn't a lot to do with how good the art is.