HexSys Grouped Quantity Attribute Plugin Problem

Hey,

My aim is to have a product with different quantities like: 50, 250, 500, 1000 and each has its own price.
No other attribute just quantity. I don´t want that 250 is just the price of 50 *5 , I need a totally different price there.

I hope anyone can help me.

Thanks and best regards,

Mare