The LLM trend lines may indicate that further research, experimentation, and investment in LLMs is warranted. But it is a mistake to assume that trend lines predict the future. Yet this is the primary evidence that is raised in support of LLMs in response to critics.

It's not at all clear that the upside gained outweighs the cost in your hypothetical scenario nor is should it be taken as a given that the trend line will continue as is for long enough to create enough upside to outweigh that cost.