Again with the critical misunderstanding of the difference between knowing the details and using monthly/das as your negotiating language and just blindly coming up with a monthly/das target without taking the time to figure out the basis of what gets you there.
No one is saying don’t negotiate off of monthly/das… They’re saying find out what that number should be based on the actual data rather than “well, I saw some other guy got something like this a month ago” that is what most monthly/das shopper do.
This thread is a perfect example. The op appears to be targeting a price off of what “feels” right. That is a very poor way to determine what to target and leaves no effective way to evaluate if the deal is any good or not.