Price per kilo app. Say you want to purchase a box of your favorite chocolates, and you have three choices: 100g for $2.99; 300g for $4.99; and 450g for $7.99.Which choice will give you the most value for your money, and how to calculate the price per kilo? Stumped? The correct choice is 300 g for $4.99.t is now easy to calculate the price per kilogram! - CostPerKg.com (Price Per Kilo) is a mobile-enabled, user-friendly website app, where you can make free cost comparisons on-the-fly using a mobile device, tablet, laptop or desktop.