How to make a quotation/price prediction for a 3D model/Drawing?

when a customer asks me what his idea would cost to make a 3D model and drawings, I run into the problem of making a price for the work.

of course I can estimate the work and determine the number of hours and then calculate my hourly rate. but how do you arrive at a specific calculation for time?

especially if the customer wants you to have it produced too? then you want to quickly come up with a model to request a quote from a supplier, but you also don't want to spend too much time in the model if the customer finds it too expensive in retrospect.

are there any tips or suggestions? ideas of productize your services or maybe you like to share your idea about it! thanks!