Heh heh, no problem! Having the thing be modular in 1-deck units is a great idea. And it looks like you've already thought of the other idea I had, which is to have the thing be connectable on all four sides, that way people can construct a deck display in any shape they want, be it square or rectangular, or round or triangular or whatever.
As for getting the product made for a decent price, injection molding is the way to go. Once you get past the tooling costs, which aren't much at all, you can crank these out for very cheap. Create a 3D model of the thing, have a few of them rapid prototyped in ABS plastic, test them out for connectivity and fit, then you can commit to getting the injection molds made. Here are some links to shops that can do the prototyping and injection molding for you:
www.approto.com
www.protomold.com
www.quickparts.com
You must be reading our minds sir, because we also had the idea to use injection molding! I've got several other ideas for variations on building the card display(s) as well different production methods, but I guess we'll see how things go. Anyways, thanks for the links!
Since you're going with a modular display unit, consider adjustments to size. You mentioned a few of your boxes were too big to fit in the display, and then there's bridge-sized to consider as well - same height, 1/4-inch more narrow. You could make the modules available in three (or more) sizes. You could even go for the gamer and memorabilia markets if you make a size that would accommodate a slim plastic card case (the type meant to hold a single card) and/or one of those sealed cases for professionally-graded cards.
Or what if I could design a unit with an adjustable grip?
It'd be awesome in my opinion, but pretty difficult... anyways, the idea has been in the back of my mind. But yeah, I'll definitely consider going with different sizes for different sized decks, or maybe even expanding this idea to other collectable items. I'm sure lots of collectors would find a use for such a display.
