Your question is a little unclear. Is your customer an end user of your product or is your customer a company in the casting industry?

If a prospective customer (aka casting company) is interested in your product (aka knocking on the door), you need to start the conversation by qualifying your prospective customer and making sure that they are the right fit for your product. After you've qualified your customer and assessed that they are a great fit, you need to reinforce the value of your product and have the prospect confirm they understand the value.

Assuming you have figured out your pricing model, then you will go through the pricing numbers with your customer and if they agree, you can subsequently send an invoice and get paid for your product. Happy to go into detail about your sales process on a call.