I hope this doesn't sound stupid, but I am having a hard time finding cake boxes big enough for my cakes. Also, the cardboard to put them on. I have searched Hobby Lobby and Michaels and Party places. There just doesn't seem to be any big enough for the specialty cakes that I sometimes have to do.
I recently ordered from BRP Box Shop by Big River Packaging (http://www.brpboxshop.com/pink_cake_boxes.html) and was very happy with their prices and quality of bakery boxes. I needed a really good way to transport a huge amount of cupcakes with separators in the boxes so that the cupcakes would not tumble around. I especially loved their fast, free UPS shipping policy within the US! The only adverse problem you or others might have is that BRP sells by the case, not just one or two boxes, etc. So, you will need room to store the boxes/separators; however, when you have enough orders of the same size cakes or quanity of cupcakes ordered, the boxes will pay for themselves.