You could charge based on some metric of use, as opposed to an all you can eat style charge. $50 is very prohibitive if I used this to automate a task that'll earn me $20/month.
The problem now is that the obvious metric ('bot runs') is too crude for a DIY bot-builder, and may stop users during development.
It's very likely our pricing system will evolve to resemble zapier's multiple tiers - they have the closest business model to ours. We're basically "The Zapier of RPA".