Let’s assume we’re talking about a phone with a touch screen - iPhone, Android, S60 5th Edition, Palm Pre, etc. - the most basic action is a “touch”, which would be ranked as a 1. Now, to me, some actions cost a lot more than others. Any time you change contexts - for example, changing to a completely new screen - would cost 5 points. Menu items would cost 2, but hierarchical menus would cost 4 or even 5 per level. Scrolling could cost 4 points per “page” of info. “Modes”, dialogs, hidden items, or stuff that changes contextually would cost even more, as I think there’s nothing more frustrating than looking for an option you knew you had seen before, only to have it disappear because of some arbitrary mode you didn’t realize you were in.
Decisions are also a cost as well. Just because a menu is easy to “use” doesn’t mean it’s easy to understand. If you’ve got seven items on a menu or 10 sections on a form, then that should cost more to use since the user has to waste mental cycles choosing something from a giant list of options.