Yes, both CircleCI and Pantheon offer a Free Trial.
CircleCI is designed for Large Enterprises, Medium Business and Small Business.
Pantheon is designed for Large Enterprises, Medium Business and Small Business.
Pricing for CircleCI Starts at $39/Month whereas for Pantheon Starts at $29/Month.
Some top alternatives to CircleCI includes Codeship, Semaphore, GitLab, Bamboo, AutoRABIT CI, Buildkite, CloudBees Core, Travis CI, AppVeyor and Bitbucket.
Some top alternatives to Pantheon includes Super, Qualified, Workvivo, AirOps, Webapp.io, OpsTech, SuperOps PSA Software, WebEnliven Solutions, DEITY Falcon, WordOps and IFTTT.