Ditto to Dave .... I started life a long time ago working in injection molding, base machine ... we'll call it a DIY entry level machine anywhere from $500K to a cool Mill. get a good machine with nozzel purges and auto hoppers, start digging ... around $5M now you're need an CNC to cut the dyes and a good programmer, starter model CNC $1.5M to the sky. Then there is tooling, dyes, waste, coolant, operators, maint. not to mention the 480V industial power for injection models and 240V three phase power for CNC's ... yep a good 10 or 20 million should get you setup ... now all you need is employees to run it all, and health care, 401K, taxes, insurance, etc etc ... ok make that 30 million and a lot of luck.
Might want to try resin casting first, still not cheap but affordable for most hobbist in the low $100 range for most everything you'll need to get started for small molds, tools, and supplies.
Bowjunky35 just posted a really good starter feature which can be found by
clicking here Dave