I didn't know about the Red Cross and its donuts. The example I've always used for this is helping a friend move.
If the friend asks "hey, will you help me move? I'm buying pizza and beer afterwards!" I will more than likely say yes, even though I can buy my own pizza and beer.
If they instead say "hey, will you help me move? I'll pay you $21.58 for your time," I'd probably bristle. Even though that might be the equivalent price of a few slices of pizza and a beer, the category has changed from showing appreciation to placing an actual value on my time, at which point working all day for $21.58 stops making sense.
If the friend asks "hey, will you help me move? I'm buying pizza and beer afterwards!" I will more than likely say yes, even though I can buy my own pizza and beer.
If they instead say "hey, will you help me move? I'll pay you $21.58 for your time," I'd probably bristle. Even though that might be the equivalent price of a few slices of pizza and a beer, the category has changed from showing appreciation to placing an actual value on my time, at which point working all day for $21.58 stops making sense.