Here is the deal, it really does not matter. Commerical truck shipments are limited to a #100 at a time. So unless, you are on truck route that delivers powder you will be limited. You might want to check with Grafs, as they stock larger kegs of powder FFL O6 pricing on primers at one time. Check with the parent of AA and Ramshot, Western Powders.
Many of the larger wholesaleer actually run their own trucks, and thus might be able to deliver larger quantities then say a commerical truck. You need to conisder reading up on what the State and Local Ord are on the storage of Powder and Primers. Check the back of free Powder Guides, as most have NFPA guide lines.