A couple of the metrics that I like to capture around vendor performance is "Number of Pricing Iterations" and "%age of Discount."

Number of Pricing Iterations or "NOPI" is a metric that I like to see on the low-side.  What NOPI measures is the number of times I go back and forth with a vendor on price.  The higher the NOPI, the more time and effort I've expended interacting with the vendor on getting to a reasonable price.  A high NOPI directly translates into wasted time and wasted resources.  If I have a vendor with a high NOPI, I have a vendor that doesn't give me "best and final pricing" the first go-around.  Instead, I have an opportunistic vendor that throws out high-sided pricing in the hopes that the price sticks.  Then, I go back to the vendor and appeal to their sense of fair play and reasonableness, only to have the vendor adjust their pricing slightly.  Then, I go back to the vendor with empirical / benchmarking data as to why their price isn't competitive, only (again) to have the vendor adjust their pricing slightly. In some cases, I have to go back and forth multiple times.  Of course, a lot of this back-and-forth can be eliminated through the competitive sourcing process (where a vendor like this wouldn't make it onto the short list).  But, in some cases, I have an incumbent / entrenched vendor that I have to deal with or a vendor that my customer has fallen in love with.  NOPI is just a nice measurement and piece of data to have available which is an indicator of the difficulty of doing business with a particular vendor.  It also opens up a conversation with the vendor about how to drive efficiency into the relationship through the vendor providing more realistic pricing the first go-around.

%age of Discount or "POD" is also a metric that I like to see on the low-side.  That may seem counter-intuitive at first...  POD is the discount from the original pricing that the vendor proposed to me.  Why wouldn't I want to get a significant discount?  Well, a high POD is similar to NOPI in a way--it indicates that the vendor has set a high price (in the hopes that it sticks) and then later offered a substantial discount--after I've "worked" for it.  A high POD combined with a high NOPI is a fairly good indicator of a vendor that could use some "coaching" from me.

What I strongly prefer is that a vendor give me their most competitive pricing the first time.  I make it clear to my vendors that, if they do, I'm not going to go after them on price.  While one of my performance measures is cost savings, I would much rather explain to my boss why my cost savings target should be lowered (because I'm getting competitive pricing on the front end) than to have a high cost savings result because my vendors are sand-bagging me on price.  I have vendors that have low POD / NOPI metrics that don't hear a peep from me on price (assuming that they also perform).  These are the vendors that I try (and do) drive business to, not the ones that offer me huge discounts after an initially high price and multiple back-and-forths.