You don't how cakes work. Cakes give you vitality buff, like vitality herb. Lasts 5 minutes after that you need to get close to it so you get buff again, its an aura around the cake. Everyone that gets close to it will get the vita buff.
And after some thinking, I think they are not too overpriced. Yes it would be perfect if they were 1-2€ per cake.
Also put them in game after one week? That is not good because after one week at least top clans will be rly high lvl all ready and wont need them as a must.