What is the approximate price for a modeler to do face posing?

I don't think that would be particularly expensive. I'd probably charge 10-25 just because it's a little unusual, less for each in bulk, and it depends on the complexity of the models and how much manual effort would go into remaking the necessary phonemes if you're using a pre-existing system for lip-sync. Some models have face bones and making the poses is relatively trivial compared to doing them by hand. Definitely helps if you have an example of a model that already does what you're looking for, so replicating it is straightforward.