If you are selling your model on a market place, then yes, comparable model value is a good starting point.
However, in this case you have been approached to sell your model, I would evaluate the price based on your time.
How long did it take? You can guesstimate this.
Then decide how much your time is worth.
You are obviously a skilled artist, so don’t undervalue yourself. Find out what other skilled artists charge.
Example: Time = 20 hours, Hourly rate = $30. Sale Price = 20hx$30 = $600
If they want exclusivity, meaning you can’t sell the model elsewhere, bump up the price a little more, say $800.
You can always negotiate, as this wasn’t a commissioned piece. You could negotiate an agreement for more commissioned exclusive work.
Remember selling on a market place such as Blender Market will give you repeat sales over time, and quite possible exceed the example above.
So don’t sell at a market place value to a single buyer, who approached you.
