Despite recent employment and education in Bookkeeping/accounting, I formerly had many years experience in purchase replenishment, stock/inventory control and demand planning. If you run a business that uses or sells stock then sourcing a product with the balance of best price and best quality is a must. So too is holding the right amount of stock; not too much to unnecessarily tie up cash, and not to little to sell out and cause customer dissatisfaction. This can be seen as an equivalance to margin on sales prices, except it is a leverage on costs. This impacts on your cash flow. This sits nicely with purchase ledger in bookkeeping/accounts as supplier contact and the relationship could be built from purchasing all the way through to payment by the same person, engendering trust. This could be important for a small business that doesn't employ Buyers as well as Bookkeepers or Accounts Assistants.