Raising prices always results in some amount of pain and frustration for some set of users. You could just start with calling your low price as an introductory

Raising prices always results in some amount of pain and frustration for some set of users. You could just start with calling your low price as an introductory offer that will be available for a limited period. You could also give extended credits to paying users who refer others who become paying users. Have the introductory price locked in for life for those who get in early. Bonus points if you can quantify what the limited period would be, instead of leaving it vague. This is how most of the good sellers do (be it a SaaS or some other content or service).