My usual recommendation to people trying to start something hardware related is to do as much as you can in the beginning to make "sales", with sales being defined as whatever you can get that proves someone would actually pay you money for your widget. Prove you have a market before you pay for expensive tooling. That process can vary, but crowdfunding is one example.
Some rough rules of thumb if all you are interested in is cash outlay:
need 2 parts: 3D print or CNC
need 10 parts: silicone mold or CNC
need 200+ parts: injection mold
If lead time to first part, part uniformity, or uncertainty about design changes are factors that might also swing you toward or away from injection molding.
For injection mold tools, assuming the part has a normal level of complexity:
2cm cube: ~$3k, 5 weeks to first shot
15cm x 5cm x 2cm: ~$4k, 5 weeks to first shot
25cm x 15cm x 5cm: ~$8k 8 weeks to first shot
First shot means the first time the tool is tested to make samples. Generally there is a sample approval and testing process you have to go through before any remaining tweaks are made + the final mold texture or polish is added. I find the total time has more to do with how organized and diligent the client is in responding, but assuming nobody drags their feet we generally can be production ready in another 2 weeks or so.
We only work with production tooling (hard steel, lasts a long time). From checking around, if you use aluminum tooling or other "cheap" fast turn prototyping stuff the price doesn't seem to be any less, and in many cases is more. Tooling made in America is usually significantly more... maybe 1.3 - 3x more.
If you only need 2000 or so for a simple part to start, and are willing to pay 2-3X the part price, Protolabs is a good option.
Another low tooling cost, low volume option that might be worth looking into is cast urethane.
However, for a 2-up mold for something the size of a game controller, with a 0.5mil shot life, with maybe a slider or two, you are looking at $8-10k at many of the molders I've worked with.