Hello, and thank you for your question.
These "paintings" from the mid-20th century are actually fine reproductions made to simulate original works. Their scale, scenes, and quality have lent to their popularity; both then and now. These are considered decorative items and as such their prices/ values can vary widely. So, their estimated value would reflect what the market might see as a general target range for such decoration. Currently, for a fine example of "Spring Lake," in excellent condition, $300-$400 would seem to be the selling target. A few years back (as with most things), a slightly higher value/ price might have been noted. Of course, If you are thinking of selling, you can start out a bit higher as you can always come down if needed. The above estimate would simply be the range in which the item is more likely to sell.
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Thank you, again.