How much sugar should go into sweet tea?

The family likes sweet tea, and seemed like it would be good for everyone if we put less sugar in the tea. So I thought I would gradually reduce the amount of sugar in the tea. We usually put a cup of sugar in a 1 gallon pitcher--so I put slightly less. And every time they noticed, and complained that the tea isn't sweet enough. A hairline less than a cup and they notice. I kept trying, and every time they noticed, so I finally gave up.