a)the lower-priced versions exist to make the higher-priced versions more appealing Works the other way round for me. But I suppose it's the same principle.

As for (b) The easiest way to achieve that might be be just to make each of the items in lots of different colours.

There's a sort of unspoken assumption that the people who make these decisions are competent and rational. I think in fact that's a highly questionable assumption. As true of business as it is of politics.