I think the current cost of 1 ender pearl per block extender/buffer is too high for what they get you. The standard block extender/buffer should be rather cheap in my opinion, and the cost should really only come once you start upgrading them (because the upgraded versions are way more useful). My suggestion would be to increase the amount of standard block extenders/buffers you get from the recipe to something like 8.

The recipes to upgrade the block extenders I think might be good as they are.