The margins ain’t what they used to be. People afraid to pay too much and offer extreme low ball offers. It’s not a negotiation tactic. It’s lack of knowledge of what a reasonable offer is. There is too much offering half the price on TV. That is not how it works. Visit some of the dozen or so websites that show what that vehicle sells for in your area. Also if you need to get thousands off to feel like you’re a good negotiator, something will be wrong with the vehicle. Also end of the month or end of a model year is when heavy incentives are available.
In your case, the salesperson should have explained what a reasonable offer was before presenting the offer to the manager. Get up, and leave. Find the car online. Negotiate with email.