It is not an all or nothing proposition. Building an app keeping in mind scaling doesn't mean you go for complex initial setups. All you need to do is make some simple design decisions to build the app so that it can scale to multiple web front-ends if need be. IMHO - this is usually the most common first step in scaling.

Also building your app thinking about a bit of scaling upfront gives you more time to work on your app, because you don't even have to setup and configure your web servers - getting an app running in Heroku is the most painless way of app hosting that I've seen.