"Cost Effective"?
You mean for the 'lectric bill?
Or replacement ballasts?
My household did get in the habit of turning off the kitchen light.
On Off On Off On Off On Off...
However, that meant the ballast(s) only last about 12~24 months.
The $$$ ballast on the closest switch fails "regularly". If fact, it does not work at this very moment. But it fails often enough I have a new spare ballast in the kitchen drawer. (how sad is that?)
Solution with more silly details:
Strange wiring in my antiquated home.
The main fixture is 4 T8s, with two 2 bulb ballasts.
Ghurd connected each pair of bulbs and ballast to its own switch.
When a ballast fails, use the other switch!
Also, usually only need a pair of bulbs instead of all 4. If all 4 are needed, turn on both switches.
Saves power 98% of the time. Saves ballast wear&tear 99.9% of the time.
G-
I don't think I would use a motion sensor for T8s.
1) Motion sensors can go off when you NEED the darn light, like standing mostly stationary at a lathe or something.
2) Motion sensors will run the light for 5-30 minutes if you go past to get an ink pen, stray screwdriver, etc.