How do kn how much to charge

Knowing how much to charge starts with understanding your costs. (labor, materials, equipment, fuel, insurance, software, and overhead) and building your prices to cover those costs plus a target profit margin typically 15–30%. You should also research local competitors to understand the market, but don’t compete on price alone, compete on value, quality, and experience. Use production rates to ensure jobs are profitable, and always price based on the outcome, not just the task. Bundling services, offering tiered packages, and clearly communicating the benefits of your work all increase perceived value. You should also, track job times, profitability, and customer feedback to continuously refine your pricing and stay aligned with your financial goals.

I live in town where you can't go 5 miles without seeing a mechanic but what I provide is unique service and fill a niche that customers need. My prices are about the same with competition BUT I provide something no one else does. Adding value to the customer and justifying my prices. Tell your customers what makes you unique.

Cost of goods upcharge ranges depending on how much the product costs you vs customer provided or what competitors charge for it.

Market research in your area will give you the best idea of how to direct your efforts.

just keep at it and don't give up.... marketing anyway possible and get your name out there

If you have an accountat reach out and they can help you understand all your costs and help you come up with the pricing.  Call three competitors and get a quote for couple services.