You can't meaningfully negotiate details and processes that weren't designed to be negotiated individually. "My LLM tells me that tapping the walls is 20% of the cost of a mini-split installation, so I'll drill my own holes and you have to charge me 20% less". Not going to happen.
This whole style of negotiation is just going to blow up in the face of most homeowners. The person trying to sell me bullshit can use an LLM to help them sell it even harder and think of the most high quality retorts to whatever my LLM tries to argue against them with.
But regardless, this arms race doesn't happen because the vast majority of people are bad at prompting models, and when you start writing prompts with spelling errors and other grammar issues, your model responds with low quality, wronger outputs just to punish you for your lack of attention to detail.
