As previously mentioned it depends of a few different things;
Although one of the most important things to do is get across what you want from your injection mold products and how you can potentially decrease costs.
One material may cost a lot more than another but it may be essential to your products design, so be sure to keep that in mind when cutting costs.
A custom design will usually be pretty costly so also be sure that there isn't already something out there that already suits your needs, check sites
Yunpeng mold answer injection plastic molding tool questions for you!