Art has **no intrinsic value**. The only value of any artwork is the *value the artist places upon it* or *what others are wiling to pay for it*.

Diamonds, as an example, also have no intrinsic value. They are price at whatever they can get consumers to pay. Buy a diamond for $5,000 and walk out of the store, turn around and walk back into the jewelers.... or go immediately to another jeweler.... it's then worth less than half what you paid for it. 

Find the right buyer and you may sell a painting from a (presumably) unknown artist for $1,000,000. But being unable to find the right buyer may mean the painting is worth $20 at the local flea market. Same painting - no intrinsic value. 

In addition, demand plays a role. How many are seeking landscape paintings from an unknown artist? How many artists out there are painting random landscapes? Will this landscape painting have more value if sold where the landscape is recognized?

There's no possible way for anyone to place any value on this painting other than the artist themselves or someone shopping for landscape paintings. 

**The best one could do is shop themselves**... see what similar paintings are being sold for and price for that same venue or sales outlet. Unlike commercial art, with fine art time spent creating is rarely a qualifiable figure which can be used to calculate pricing - those purchasing fine art do not care if it took 10 minutes or 10 years to create the artwork.