[phillmv]

Heroku's kind of in a sweet spot.

They already charge an immense premium over your own fleet of micro to large instances, but by the time you rack up enough dynos for it to make sense to spend the necessary weeks migrating your infrastructure there's a good chance that replicating the environment with your own in house version (30+ instances?) is non trivial enough to be scary.

Once you're over a handful of dynos, the sunk costs and uncertainty will keep you there until it becomes totally ludicrous.