Here are some tips from a local consultant who is experienced in both international trade and technical issues.
The cost of a basic mold is about RMB50,000 to RMB100,000 (8,000USD to 16,000USD).
The prototype (mock up) is not as nice as it comes from the mold, to develop one of this kind of plastic prototype is usually RMB15,000 (3,000USD)
The set up fee to run a basic PCBA at a PCBA supplier is usually RMB3000, but they expect you to place a big order in the future. The design fee (prepare documents for PCBA production) is usually RMB30,000 and they will also charge you for their work which is about RMB50,000, but they will refund you the fee for their work (8,000USD) as soon as your order quantity reaches 10K PCS, they will not refund you the fee that they spend on the material and PCBA sample cost no matter what.
To develop a new product in China, you need to define all your requirements in documents such as Word, picture and video. When the suppliers receive this document they think you are serious and they are more willing to spend some time to study and give you a rough quote, and sometimes they will convert your documents into their PCB sketch or any drawings they use. These requirements include all the features you want in your product, as well as the look of the product, the suppliers will then tell you if they can realize that.
The deliver lead to develop a new product is usually 30 days for a simple one, it can be 45 to 60 days depending on how complicated it is.
Payment: the suppliers need 50% down payment to start the project, and 50% right before they deliver you a sample and document (You might want to come and see what sample they develop and if it works for you, or you can hire me as your inspector to have a look on your behalf, then I will perform a FAI service for you, I will take both pictures and videos and share with you online.)