Comment by lolinder

If you can actually offload substantial CPU cycles to the client, yes, you'll save server costs. But the SPA hype has led to a lot of SPAs that work like this:

> User clicks a tab. A request to server fetches the JSON data for the tab. Client renders it to HTML. User fills in some fields and clicks submit. A request to server sends the JSON form data and gets a JSON response code. Client shows a confirmation screen. ...

In this case, you're not saving much by templating JSON on the server instead of just templating HTML.