Hi,

ICO Price
Pre-sale: 850 GGS per ETH during

Main sale: 750 GGS per ETH for first hour
650 GGS per ETH during first week
600 GGS per ETH during second week
550 GGS per ETH during third week
500 GGS per ETH during fourth week

Sorry but it is not clear what do you mean on calculation of the investment... Could you please specify your question?