The comparison, done properly
The discount is easy: 15 percent of $60,000 is $9,000 saved. The cost of money is the number funders do not volunteer: the total dollars repaid on a $60,000 advance or loan, minus $60,000. Ask for it; it is the only figure that makes this decision possible. A term loan over six months might cost a few thousand dollars; a factor-rate advance at the higher end can cost more than the discount. The same purchase is a good idea with one product and a bad one with the other.
Then the carrying cost. Six months of stock takes space, insurance, and the risk that demand shifts, a product is discontinued, or a season ends with a third of it still on the shelf. Owners who have done this describe the unsold third as the real price of the discount.
When it clearly pays
Stock that you will sell at a known rate — a consumable you reorder every month, a part you fit every week, a product with two years of steady sell-through. A discount on a staple is a discount on money you would spend anyway, and if the total cost of the money is less than the saving, the arithmetic is simple. It pays best when the money is cheap: a line of credit drawn for the purchase and repaid as the stock sells, or a term loan with interest that stops when you repay.
When it does not
Fashion, seasonal goods, anything with a model year, anything you have sold for less than a year. A discount on inventory that might not sell is a bet, not a saving, and the borrowed money has to be repaid whether the shelf clears or not. And a discount funded on a fixed-factor advance repaid daily over six months is often a wash at best: the money costs about what it saves, and the business carries the debit through the months the stock is still on the shelf.
The version that usually works better
Ask the supplier what discount they will give on three months of stock rather than six, and whether they will give terms — net-60 — on the larger order instead of a discount. A supplier who wants the volume will often do one or the other, and terms cost nothing. Borrow only for the piece that neither covers, on a product whose total cost in dollars you have seen in writing before you sign.