I worked for a market research company once (reasonably well respected, in their field) and we still had a hellish time getting employees to talk to us for money. Many staff are not comfortable with talking about their area of expertise (which is obviously related to the company they work for) outside of the confines of that company, or are certainly not going to accept cash for doing so off the books even if that is donated to a charity organisation. Additionally, many companies are not really set up to handle contracting out their already occupied employees (especially senior staff) for an hours salary.

Actually, thinking about it most of the reputation we had was in speaking to smaller owner-operated businesses where the owner or self-employed associates were free to speak to us and could gauge the benefit to themselves from doing so (our interviews were often on behalf of larger companies testing the market for product ideas, so they would get the satisfaction of providing feedback and even getting advance notice of what may be on offer)

anyway, what I'm saying is.. it can be difficult and time consuming to arrange that but it is possible to get somebody else to do the drudge work.