I used to buy the Ultrapro cases by the case lot, both the single deck (5) and the dual deck (100). The individual plastic box by the case lot, qty 100, drops the price dramatically. I found the lid does not quite fit tightly, ie. the lid drops off, you have to use a rubber band to keep the lid on. That wasn't too much of a problem the way I displayed them. If you are using these boxes for long-term storage beware:: they do not filter out UV light. You will have to control the environment in other ways. They also emit a plastic smell that can build up if the boxes are in another container or display case. You will need to provide for some air flow.
As far as using a box that is more expensive that the deck of cards, I have figured out that between my (1)protective plastic boxes, (2)display cases, (3)environmental controls, and (4)database costs, a dual deck setup costs me $13.00(USD) above what I paid for it. That is over the course of 5 years. A single deck, which is not common for me, costs $10.00(USD) in addition to the deck costs, That is excepting my garbage decks that don't get any special treatment, they are simply thrown into a box, awaiting disposal.