This looks like a serious agency, so I'm stuck on the question of why the free tier is so important to them versus simply paying for Heroku. Surely doing a mass migration to a new PaaS just to claim a small per-project savings is a dubious proposition given the inevitably of a future rug-pull from wherever you migrate.
On the other hand, if you're an individual with a bunch of small projects and you want to host them economically, then standard VPS hosting is going to give you a lot more bang for your buck.
Post author here. We are of course using paid dynos for any business applications. Free tier only makes sense for hobby projects and quick experiments. There's no free lunch in the long run.
On the other hand, if you're an individual with a bunch of small projects and you want to host them economically, then standard VPS hosting is going to give you a lot more bang for your buck.