That's fine for simple one-off apps that don't require serious infrastructure, but Heroku is just ridiculous with its pricing if you need any kind of complexity.

I can burn through 1GB of Redis cache really easily; on Heroku, that's $200 a month. On AWS a cache.t2.small instance is $16 a month. The same for SQL space, disk storage, etc., once you're past a certain point Heroku becomes just unbelievably expensive.