The Carb Manager app is free to download. Some of the basic core features are free to use. There are also premium features (in-app purchases) which range in price from $4.99 to $39.99. 1 month of Carb Manager is $8.49. 3 months of Carb Manager is $16.49. The $39.99 charge is to use the premium features to 1 year.
See more about Carb Manager Premium at carbmanager.com/premium.