When you order five bottles (either the capsules or the extract) you get an extra bottle of capsules at no charge. If you order in bulk, I believe you can get 1000 capsules for $550.
Yes, I would advise people to stock up for multiple reasons - one being that as word gets out there are going to be some folks who see oleander as quite a threat. For that reason I think it is also a very good idea for everyone to get themselves a couple or more plants to grow their own just in case. Of course you do have to know what you are doing and follow directions, since oleander is quite toxic in raw form (but not so when properly boiled, strained, condensed and preserved as per directions).