You can’t have a collaboration over price. Price is always win-lose. What you gain the other party loses (or pays) and vice versa. There is no way to grow the proverbial pie when it comes to price. Unfortunately as luck would have it, price also seems to always be a very important element in negotiation. 
If you constantly equate all other trading variables back to price you will, whether you like it or not, create a distributive environment. The key is to shift your focus to profit! Instead of thinking in terms of cost or price think in terms of value. The ability to incorporate intangibles into a deal is what separates a skilled negotiator from the average bazaar merchant (although hard bargaining also takes a certain type of skill). The ability to link variables other than price to create incremental value is where all the value is in negotiation.
Having said that (stealing a line from “Curb Your Enthusiasm”), there is a time and place when a good old fashioned price negotiation is just what the situation calls for, so don’t be afraid to shift gears in either direction. After all, negotiation is all about the circumstance and your ability to determine what is appropriate.