This question is an opportunity to show how you understand the 'whole picture' of the role. The term "great" is reserved for those that inspire others to also become great.
A great Purchasing Manager (PM) can be described by ten attributes:
1 They make decisions based on the best interests of their employer
2 They are collaborative - others in their organization are aware of their actions and participants in the process
3 Price is never the sole factor in making a purchasing decision
4 A great PM measures their performance and shows their value to organizational management
5 A great PM treats their suppliers fairly and does not take advantage of them
6 A great PM embraces new technology as a way to improve their work
7 A great PM negotiates knowing that the person across the table may some day be a partner or an employee of their company and shall be treated as such
8 A great PM knows that the economy is global and never makes assumptions that they know every supplier in the world
9 A great PM builds a program and enable team members so that they can carry on should a crisis arise, the PM leave, get sick or worse
10 A great PM will continue to improve their skills and ultimately deliver beyond expectations"