Gmail users who utilize the Web e-mail service to back up data on their home or work PCs and are approaching its 3 GB limit level may appreciate Google's additional storage offering. However, the extra space comes for a price: Users could buy as little as 6 GB of storage for $20 per year, or up to 250 gigabytes for $500 annually. It will also offer a 25 GB plan for $75 and a 100 GB option costing $250.