Keep being realistic. the buyer is the first who should already wonder about such a number, if you have not already a release procedure in place.
Latest the vendor would not just accept such order, your order will probably be blocked by the credit limit which is setup for you. Your order would probably exceed the annual production capacity of your vendor.
And with the right MRP parameters (MRP view 1 to 4 in material master) in place SAP could not itself order that much, and if you create requisitions manually in SAP then you may need to some controlling instances like release procedure to prevent such orders.