You pay 4 ATP (grey flask) plus 2 ATP to get 2 Carbs.
Then you pay 1 carb to get 6 ATP.
In the end you gain 1 carb.
In addition, a player is limited to one grey flask per turn. Not much of a snowball, especially if your opponents decide not to let you get both in a round. And you can use the second grey flask to snatch the start player marker from the current start player.