In ideal world (utopia) it should be based on expected revenue or it could reflect (time) costs of model creation. Maybe this worked in 2010 very well.
Nowadays the main aspect is competition. If you will create model of "Iphone 13" and set the price to 80$ your model will be probably never sold - you should set average price (or slightly higher) of specific model category.
So your aim should be to do original (unique) models with low competition in other words try to find gaps in 3D marketplaces catalogues.
If you will create unique model or model with some additional value (extraordinary quality/complexity, unique texturing style or unique design concept) then you can make pricing strategy based on expected revenue or time consumption with model creation.
