What is the cheapest alternative to the Retrospective Software Tool Parabol?

The more affordable alternative to the retrospective software tool Parabol is Echometer, depending on the size of your team. Parabol charges $8 per team member, while Echometer charges per team. Since Echometer costs $29 per month for a full team, Echometer is cheaper if you have more than 3 team members - which is the case for most teams.