I think it's better for now to use LLMs to generate the bulk of a task, then have the developer clean up and integrate rather than trying to get the LLM to do 100%.
That said, you can accomplish a workflow like this with Plandex already by piping output into context. It would look something like:
plandex new
plandex load relevant_context.ts some_more_context.ts
plandex tell 'some kind of complex task'
# ...Plandex does its thing, but doesn't get it 100% right
npm test | plandex load
plandex tell 'please fix the problems causing the failed tests'
I haven't done too much digging into exactly how much people who are using Plandex Cloud are spending, but I'd say the range is quite wide even among people who are using the tool frequently. Some are doing small tasks here and there and not spending much--maybe they're on track for $5-10 per month, while I'd guess some other heavy users are on track to spend hundreds per month.