Blocksworld Premium is the only pack that costs real money. What's special about it is that all the blocks it contains are coming in INFINITE quantity, which explains the 7,99$CAN price tag.
This pack now contains around 182 pieces. This number will increase each month along with newly released action blocks.
For now, the pack contains ALL the building blocks that are in the "Blocks" section, ALL the action blocks (new ones are added each month), most of the "Decoration" blocks and many textures and sounds.