How much EGCG and caffeine can specific amount of water absorb from tea leaves?
3x tea would not mean 3x extract

But it is going to be close to 3x for small amount   

Water is a good solvent for those chemicals but there is a limit  

The solubility of caffeine is 2 g/100 mL at room temperature (by weight about 1 : 50).
66 gram / 100 mL at boiling.   

A coke is 20 mg (milli 1/1000) 12 oz.
The caffeine we drink is not even close to saturation.  

In extraction you equalize the mole fraction with a fudge factor.  I don't know where to find fudge factor for tea.  But it would favor the water.  

A dry tea leaf is about 3% caffeine. Getting the caffeine out with boiling water you can pretty easily get up to saturation at room temperature. But you would need quite a bit of tea.  2 g caffiene would be 66 g of tea.  A tea bag is about 2 grams.

In a commercial extraction they would use a solvent like ethanol.