It's almost always better to pay more for the smarter model, than to potentially give a worse player experience.
If they had 1M+ players there would certainly be room to optimize, but starting out you'd certainly spend more trying engineer the model switcher than you would save in token costs.
Not only that but I think our selling point is rewarding creativity with emergent behavior. I think baked dialogue would turn into traditional game with worse writing pretty quick and then you got a problem. For example, this AI game here does multiple choices with a local model and people seem a bit mild about it.
We could use it to cache popular QA, but in my experience humans are insane and nobody ever says even remotely similar things to robots :)
[1] https://store.steampowered.com/app/2828650/The_Oversight_Bur...