Small shops almost always price too cheaply. Not taking in to account all the "true" costs of doing business. Don't use someone else's prices for your work. They will have different costs than you. As for the "formula systems" you might use them as a check to make sure you didn't make a gross error but never for your pricing. There are many things you need to charge for that often are forgotten. Design time, drawings, consultations, materials ordering, time value of money, replacement cost of equipment, tooling, packaging and most importantly profit. What is your plan? Do you intend to ever become larger? Add equipment, additional education? All these need to be covered. How did you figure out your shop rate? Rent, utilities, wages, book keeping, tooling, replacement equipment, trash, expendables (glue, screws, sand paper...) cleanup, etc. How do you figure the time you will spend? Does it include all of your time? Even once the drawings are done and in the shop, there is time spent in addition to the actual machining and assembly. Setup time can be significant and exists for every operation. Material handling.
What do you think you are worth/ $25 - $40/ hour minimum. Shop rate a minimum of $50/hour. Don't give your life away.