Indeed, I think "not to count the cost" fits rather well into the way I stated it originally - I don't count the cost unless and until I actually find it's costing too much and I'm actually starting to become unable to keep giving.

I can see your point; I think what would happen in practice is that I wouldn't really notice unless someone pointed out to me how I could be doing much better, and after they'd done that everything would be changed by the fact that it had been made explicit. For a start I'd probably feel guilty about whatever decision I made; the element of "my time/effort" would become a conserved quantity which someone had to lose some of whenever someone else won some; and I suspect the whole thing would be generally unpleasant for most of the people involved...