Bunnie Huang spoke at one of the RISC-V summits on this topic.
Indeed - and this is exactly the point of ISA licensing (and IP blocks): to make it sufficiently cheaper to just license the ISA or IP blocks instead of developing the product from ground up.
I am not convinced that competition is always a good thing here: lots of competitors lead to shrinking margins. This means less money that can be invested into innovating by the respective companies.
Unless we can automate the chip making process. Think of it as the chip version of PCB micromanufacture or 3D printing. At some point someone will make a business out of making boards and placing all the components for you. The trick is to do it without any retooling and no humans involved.
What is the manufacturing cost of a wafer full of, say, CPUs? If we can all get our designs in there, we can share the manufacturing cost.
This is called "multi project wafer" or "shuttle service" if you want to look for it.
Actual prices are pretty rare, but I happened to find some: https://nmi.org.uk/wp-content/uploads/2016/11/01-Easy-Access... ; those line up with what I've heard. $25,000 for a few chips from the MPW service, or $100k for your own mask set then $1-2k per wafer.
There are lots of things that cost money in hardware design, and ISA licensing is a very small part of them.
Edit: I wonder if I should do a rather confrontational blog post telling people why Open hardware is never going to be the free lunch that open source software is..