Sorry, I see how my post lacked sufficient clarity.
The idea behind a cheap UI is not constant change, but that you have a shared engine and "app" per activity.
The particular workflow/ui doesn't need to ever change, it's more of a app/brand per activity for non-power users.
This is similar to how some apps historically (very roughly lotus notes springs to mind) are a single app but have an email interface/icon to click, or contacts, or calendar, all one underlying app but different ui entry points.
The idea behind a cheap UI is not constant change, but that you have a shared engine and "app" per activity.
The particular workflow/ui doesn't need to ever change, it's more of a app/brand per activity for non-power users.
This is similar to how some apps historically (very roughly lotus notes springs to mind) are a single app but have an email interface/icon to click, or contacts, or calendar, all one underlying app but different ui entry points.