I'm the head of R&D at Rev.ai and this is exactly what we've seen in ASR. We started at $1.20/hr, and our new models are $0.10/hr in < 2 years. We have done human transcription for ~15 years and the revenue from ASR is 3 orders of magnitude less ($90/hr vs $0.10/hr) and it will likely go lower. However, our volumes are many orders of magnitude higher now for serving ASR, so it's about even or growth in most cases still.
I think for Mistral to compete with Meta they need a better API. The on-prem/self-hosted people will always choose the best models for themselves and you won't be able to monetize them in a FOSS world anyways, so you just need the better platform. Right now, Meta isn't providing a top-tier platform, but that may eventually change.