I have a feeling that you're going to be much better off with loose leaf tea here. Teavana claims that their mate tea is good for 25-30 t/2ozs or ~15 cups. Considering that you can brew it 2-3 times, you can get 30-45 cups of tea from 2oz of dry tea.
Condensing a Mate into a syrup you'd need to be able to concentrate it to the point of 1 oz making 45 cups of tea in order to get even an ounce of weight savings. That means that you'd have to condense 360oz~300oz of liquid tea into a single ounce.