Cost can be prohibitive for scaling an app from a proof of concept to a working prototype. Especially for something that can't or won't be commercialized later.

Cost can be prohibitive for scaling an app from a proof of concept to a working prototype. Especially for something that can't or won't be commercialized later. For instance, I'm working on a web app to visualize a particular subset of twitter activity. Scaling the database to cope with performance demands may prove challenging on free project tiers.