I have been waiting for weeks to order my GM screen because I also want to get a second set of custom dice (since one set does not even suffice for the most basic rolls), but they are currently sold out. When will they be available again?
A discount when buying two or three sets at a time would be nice. I have no idea what the costs are for manufacturing dice, but I find it a little funny that two sets of dice (which, as you say, is the minimum) is the same price as the whole Boxed Core Set.
Dice with fully custom sides are expensive. These are not being mass produced. Q-Workshop dice that are fully custom are not that much cheaper and they are marketed towards all role-players, not just players of one particular game... It's a fun option, and not necessary. Another way to look at it is "These sweet hardback books don't even cost as much as two sets of dice?!" Does that help?