I'll have a go at answering, tho' I am not an oracle.
A scene is defined by physical location.
A location is defined (in broadest terms) by the need to transport equipment there, setup of equipment, the shoot, then breakdown and removal of equipment.
In practical terms, just shifting the camera or turning it around so it looks as if you're in a different location would still be classed as a new scene. Forward planning to maximize effective use of equipment in a physical location obviously saves time and money.
Should a screenwriter consider this? I think so, especially given that so many prodcos are only interested in limited location scripts. And big budget prodcos will still think in terms of cost of movement/setup/breakdown.
Of course you could break down any SCENE to any number of different SHOTS for each action sequence in the scene.
If we define your average screenplay as being around 100-120 pages, then 50-60 scenes wouldn't be unusual, given an average of 2 minutes per scene.
Hope it helps. If I'm wrong, feel free to correct me.
-Derek
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