Posted this once until it told me I wasn't logged in.
Anyway, back in college while putting up with advanced economics, I recall the "laws of diminishing returns". When you do the search it's more tied to production. However, if you think of it as a filter so to speak, you could use it for a "cost benefit analysis" for say markets, high mileage, max returns, or utilization on a given need (wants won't work for this thought). Just about any person has a "Threshold" on any given subject and need.
Now granted, I was watching our German Shepard's chase fish in the pond when this thought occurred.
Hope everybody has a good hump day tomorrow..............
PS...Relates here to buy or sell