Pails will always be cheapest for volume. Plus HPL bills actual cost only, so if you have a UPS account be sure to check your rate to compare; and they will drop ship to you. Call Mary Jane @ (815) 932-3288 to discuss.
UPS will charge an extra fee for shipping a "bucket" (anything that's not in cardboard box). They also add a hefty surcharge for pieces over 50# but that shouldn't apply to a 5-gallon bucket.
Tried ordering 7 quarts of Premium Passenger Motor Oil their online retailer and shipping is $80 to Honolulu, Hawaii. Passed and bought 2 5 quart jugs of VRP for less at WM.