Yes, all of the premium colors and other upgrades are more costly – the premium colors for the classic cases are True Red and Silver Gray. For the compact cases they are Carolina Blue, Light Blue, True Red, Industrial Gray, and Off-White/Beige.
One reason – there are paint mixing and tooling/setup costs for the lower volume colors being spread out over very few cases so the costs are higher. Different factories handle powdercoating for the compact and for the classic cases; they do not share costs or materials. The other reason is that the pricing for all of the accessories and upgrades is higher to help reduce the price increases I would have to pass through to all regular keyboards due to significant raw material, labor, and shipping increases (this was also discussed on the forums last year). The goal is to keep the base keyboard pricing from going up as much as possible, though future price increases are unfortunately expected across the store at some point this year.