How to charge for Solidworks models, some examples?
for time, difficulty, aesthetics ..?
Here some answers from the previous questions in GrabCAD. Some Answers are pretty old but you should get an idea about some factors that you are looking for.
One other "trick" I would try is to find some local CAD service providers and ask them for a estimate for same set of models. Make a table about your estimate in comparison to theirs and you will know if you are estimating way too high or way too low.