A subscription is interesting when you conduct multiple survey projects each month or when you expect considerable volumes of respondents and / or emails. You pay a fixed amount per year for an unlimited number of surveys supplemented with a package of respondents and emails.
The calculator on the Pricing page guides you to the subscription model that best fits your needs. The calculator recommends the most interesting subscription model, based on your estimated number of respondents and emails a year. The calculator takes extra packs into consideration when making a recommendation.