IDEA: Ask vendors for their delivered price and ‘pickup’ price, then, when available, assign your trucks to pick up purchases.

Ask your vendor how to cut your costs.  One of the methods he may be able to help you is to alter his price for your truck pickup at his dock. First ask for delivered prices, then request prices if you pick up the load with your trucks.  Offer to do this and compare prices. Your new price for materials you buy from him should drop without freight costs and now yield a cost savings (assuming your freight costs are less than his).  Know where your drivers are at and send one to pick up an order when he is in the area because it is most likely worth it.