Because you are designing and producing a one-off items. Basically, you are engineering a tool which allows you to shoot molten plastic at high pressure into tiny cavities, with tolerances smaller than a tenth of a millimeter for the end product. That's not at all trivial and therefore unaffordable, unless you are building molds which will be used to create tens, if not hundreds of thousands of copies.
The cheap option is to reuse an existing mold, mostly by asking a manufacturer to create keycaps in an existing profile, but in a color of your choice. That's what almost everyone in the keyboard industry does.
I agree with the OP. Either they have to sell tens of thousands of this keyboard, or it is going to be priced in the high-hundreds or even low thousands of $.
I have a keycap in mind, but what scares me is a mistake in the design. I give the model to the manufacturer, they create a mold, do a sample run and it turns out e.g. the stem is 0.1mm too wide, so it is too loose. Then make another mold, this time it is 0.05mm too narrow etc.
They gave me advice to create a model and order a 3D print to ensure it fits right, but I am not sure if 3D print will have a good enough precision.
When I was 3D printing at home I was never able to get exact dimensions - print was either 0.99999x scale or 1.005x scale etc.
I fear that a simple thing could turn out into multiplies of £10k and months of back and forth.
The cheap option is to reuse an existing mold, mostly by asking a manufacturer to create keycaps in an existing profile, but in a color of your choice. That's what almost everyone in the keyboard industry does.
I agree with the OP. Either they have to sell tens of thousands of this keyboard, or it is going to be priced in the high-hundreds or even low thousands of $.