Is Appeton Weight Gain really effective?

I watched a Tv commercial which is a weight gain milk powder branded as Appeton Weight Gain. I searched for it on a store and I was surprised by its price. A 450g of it costs more or less 800 pesos.

Now, I wonder if it is really effective because I am willing to spend money just to gain weight (because im embarrassingly skinny!!!).

So is there anyone here who already tried the product? Is it really effective for you?

Thanks for those who will answer me