meeotch wrote:this is 2009! We put people in space! How can we not match two different lots of purple plastic by simply putting a constant amount x of purple pellets with a constant amount y of abs plastic for each batch and get standard Lego purple?
I think the idea is that yes, they could
do it, if they wanted to shell out the money, but then it's not economical. I mean, purple matched for years prior to 2004, so they can clearly do it if they wanted to. But my guess is that if they did so, then you'd have to pay a whole lot more for those elements, and your casual Lego buyer won't understand why they had to suddenly pay twice the price for a purple set rather than, say, a blue one.
As for why purple is tricky, I would guess it's because it has a tendency to not be as chemically consistent throughout the molded bricks. I know with some dark green elements molded in 2007 (or thereabouts), the upper-left corner of one side of a rectangular brick would be a different shade of green than the lower-right corner, and so forth-- and that's within a single element! I expect that whatever the properties are of the purple dye, it's harder to deal with in their molding process than other colors-- possibly resulting in streaks, color blotches, inconsistent runs, etc.