Honestly, going through YC you get a bunch of Heroku credits. You also get AWS credits but getting a production app on Heroku is very simple, especially with rails. I also have to build and manage fewer parts of the infrastructure/deployment when you are trying to scale up and down. I don't think it's that expensive if you have optimized parts of your stack. Use web for only serving API, single page app, optimized assets via CDN etc.
Extend vs Mixins.
For Picplum we are building multiple front end's that use the same models and view logic with slight modifications. For example on our new homepage (coming soon), you can upload photos, add recipients and send out photos without having to goto the app. This is our new on-boarding process. Extending makes a lot more sense her. Homepage Batch view vs App batch view, Homepage Recipients vs App Recipients.
Require.js
We are still in the middle of figuring out a stable production setup with require. It helps you structure your Backbone app more efficiently. The tough part is to figure out how to bundle your js files effectively. You probably don't want every single JS file loading asynchronously since there can be 20+ files just for the homepage.
* why do you choose to extend views rather than using mixins?
* what was your experience with requireJS aside from your rails problems? Did you find it helped development or not?