Most people won't require every addon, and there's a free or cheap option in every case. Yes, you can spend "hundreds of dollars a month" but not easily
2 x processes + 20GB database + unlimited bundles + SSL ($20-100/month depending on your needs) == $91-$171/month. And that's for just two thin processes with a few extra features that are generally required for most apps.
It jumps to more than $200 if you want just one more Thin process or a background worker, etc.
I'm not saying that there's anything wrong with Heroku's pricing, but I wouldn't considering it a "cheap or free web-based tool".
2 x processes + 20GB database = $51/mth
Most people won't require every addon, and there's a free or cheap option in every case. Yes, you can spend "hundreds of dollars a month" but not easily