The point of having an option clause in the contract is to the buyer can get a firm price, for some period of time, if they decide they want to buy more units. For the vendor, the point is have a leg in the door for future purchases, to gin up some additional possible business and to help with future production planning. Without the clause, and additional items purchased by the buyer are subject to another round of competitive bidding, which is time-consuming and the buyer might not find anyone willing to meet their terms a reasonable price and the vendor might lose the bid to another vendor.
