I agree that's a big part of it. I remember on the big May 3rd release, Darth Maul was scarce even though it was evenly packed. Fortunately there was enough stock that people didn't panic and in time Hasbro responded with solid cases of Mauls.
That brings me to an idea: Maybe retailers could have the option of ordering solid cases of figures. Apparently it's common practice overseas. This would be great because as soon as there's an increase in demand for a figure, a retailer could order more. Naturally, there would have to be a minimum order of assorted-figure cases first.