Part of what a product manager does is to help define the sales process for a product. Not only does she profile the prospective buyers of the product, but she gains an understanding of the key stakeholders who collaborate to make buying decisions.
A college student may consult with parents before buying a car, since in some cases the parents actually pay for it. In a business-to-business (B2B) sale, the decision to buy may require the collaboration of executive, technical, and user buyers.
How a salesperson most effectively can approach a sale depends on the potentially complex processes and interactions that customers use to make their buying decisions. A product manager who has researched these processes and interactions should work with the sales team to design the sales process that works best with them.