Presenting the same option in different formats (or 'frames') can alter people's decisions.
Research in 1981 (link) told us that people choose differently between the exact same options if the options are presented differently (take a look at the Framing effect article on Wikipedia and the examples shown there).
Take a look at the way you present options to your users. What is the 'story' around each option and is the option you'd like people to choose framed in a way that it's most likely to be chosen? For example: if you like people to subscribe to something for a small periodical fee, it helps if you can place the amount in a frame that immediately makes sense to people like 'Subscribe now for less than a cup of thee a day'.