Sierra is free ship, bobs is not.
If I had more than one bike i'd buy direct from an oil company like I used to for Amsoil when I had several vehicles with same oil type. You can buy direct from K&N or NGK sometimes for same if not better deal than buying through a reseller. When I had a K16, i used enough oil it warranted buying it in bulk.
I specifically avoid doing business with Amazon whenever possible, they are not a good company and I refuse to support them.
Resellers for NGK MC spark plugs would upcharge by as much as 25 dollars per a plug, it pays to be a smart shopper sometimes.