The salesperson who tells the prospect, "Since the cost of this line of plastic utensils will increase next week, can I place your order for the product today?" is using the standing-room-only close.

The standing-room-only close is a technique in which the salesperson creates a sense of urgency by informing the prospect that the product is in high demand and will sell out soon, hence they should place an order immediately. In the given scenario, the salesperson is creating urgency by informing the prospect that the cost of the product will increase next week, hence they should place an order today, which is an example of the standing-room-only close.