As far as I know, in Magento there is no possibility to limit the quantity of the product purchased.
So you can put some special price for the products, but you won’t be limit the general quantity to no more than 12.
But there is the possibility to set tier prices for the products. For example, the cookie originally costs $1, but if the person purchases 12 and more variants of that cookie he can get each for lets say 75 cents.
I guess grouped product is more user-friendly for that situation, since there quantity will be seen next to “Add to cart” button, check the screen-shot attached.
Click thumbnail to see full-size image