Say one lone developer gets a bit carried away with verilog and ends up with a description for a chip. I know there's an odd lot style of thing where you can get your chip drawn on a wafer along with a load of other chips from other people. There's probably a way of getting someone who knows what they're doing to attach wires to it, wrap it in plastic or whatever else is involved in "packaging".
Where does one get started with that, and what's the ballpark cost? I'm assuming a fair amount of the OP's $100k is SiFive labour, but I don't know how to guess whether a half dozen custom chips in some sort of packaging is of the order of 10s of dollars or 10s of thousands.
(edit: I've done a lot of software near hardware and have a vague idea that uploading the data to tsmc was called "tape out" and involved quite a lot of money, but I also vaguely remember talking to someone at a conference who had chips made as a hobby so there are some pieces missing from my mental model)