The good ARM designs aren't free either. The big difference is that you'll always be stuck paying Arm (either for whole ARM cores, or a licensing fee for your own design), whereas with RISC-V there can be genuine competition between companies offering performant RISC-V IP.

In the MCU market the compute core is already an off-the-shelf drop-in component. Just look at the RP2350: in addition to its traditional ARM cores they also last-minute dropped in two RISC-V cores because it was so trivial to do - and you can select which set is active via a boot-time firmware flag. I very much doubt we'll see that kind of flexibility with high-end client compute, but with the switch to separate compute chiplets we're not far off already!