I don't have experience in a lot of negotiations but I have used similar methods many times. I bought a bike a couple days ago and got them to throw in a few extra things for free. I didn't negotiate the price of the bike but I made a point of needing a light and a helment.
First, I asked for a light that would be go great with the bike and the sales person put one he had laying around on the bike. I said it looked great. Then I asked for a helment and found one for me that I liked. I put on the helment and did a test ride with the bike. I told him I'll take the bike. Then I asked, how much for the helment & light? He gave me the price. I said "That's not bad but honestly, I don't have the money for everything. What can you do?" He offered to give me 20% off the helment & light. I again said that was a great deal but couldn't do it. A few more back and forth and me throwing in that I would need another bike (for my gf) and wanted to come back and buy from him, he eventually threw in the light and helment.
What I knew was roughly how much profit they were making from the bike. I knew roughly the mark up of accessories and I knew how they wanted to sell the bike.
It worked out really well for me and the business. I love the bike and the business now has a new loyal customer.
First, I asked for a light that would be go great with the bike and the sales person put one he had laying around on the bike. I said it looked great. Then I asked for a helment and found one for me that I liked. I put on the helment and did a test ride with the bike. I told him I'll take the bike. Then I asked, how much for the helment & light? He gave me the price. I said "That's not bad but honestly, I don't have the money for everything. What can you do?" He offered to give me 20% off the helment & light. I again said that was a great deal but couldn't do it. A few more back and forth and me throwing in that I would need another bike (for my gf) and wanted to come back and buy from him, he eventually threw in the light and helment.
What I knew was roughly how much profit they were making from the bike. I knew roughly the mark up of accessories and I knew how they wanted to sell the bike.
It worked out really well for me and the business. I love the bike and the business now has a new loyal customer.