Earlier quoted context omitted.
CPU compute is infinity times less expensive and much easier to work with in general
Less expensive how? The reason GPUs are used is because they are more efficient. You CAN run matmul on CPUs for sure, but it's going to be much slower and take a ton more electricity. So to claim it's "less expensive" is weird.
Even if utilisation weren't a metric, "efficient" can be interpreted in so many ways as to be pointless to try and apply in the general case. I consider any model I can foist into a Lambda function "efficient" because of secondary concerns you simply cannot meaningfully address with GPU hardware at present (elasticity and manageability for example). That it burns more energy per unit output is almost meaningless to consider for any kind of workload where Lambda would be applicable.
It's the same for any edge-deployed software where "does it run on CPU?" translates to "does the general purpose user have a snowball's chance in hell of running it?", having to depend on 4GB of CUDA libraries to run a utility fundamentally changes the nature and applicability of any piece of software
A few years ago we had smaller cuts of Whisper running at something like 0.5x realtime on CPU, people struggled along anyway. Now we have Nvidia's speech model family comfortably exceeding 2x real time on older processors with far improved word error rate. Which would you prefer to deploy to an edge device? Which improves the total number of addressable users? Turns out we never needed GPUs for this problem in in the first place, the model architecture mattered all along, as did the question, "does it run on CPU?".
It's not even clear cut when discussing raw achievable performance. With a CPU-friendly speech model living in a Lambda, no GPU configuration will come close to the achievable peak throughput for the same level of investment. Got a year-long audio recording to process once a year? Slice it up and Lambda will happily chew through it at 500 or 1000x real time