In which case the LLM contribution to the $10K/month is equivalent to hiring a mobile developer to build such an app which (given the implied simplicity) should be a few thousands one time cost. Not the $120K/month implied by PP. And don't get me wrong, paying a few dozen dollars to get a few thousand dollars worth of software is quite the value.
As an example I could imagine a clothing brand wanting an app that customers can install instead of using their phone browser. $10k/month in that context isn’t as surprising or impressive.