Hi Mayra,
I have made a few of these cakes. I use the heavy duty cake mold and it works out beautifully. I based my pricing on the current market in my area and the amount to cover my cost. Depending on how the cake is cut, this will determine the amount of slices you end up with. I charge by the slice and different amounts for buttercream only, buttercream with fondant decorations, & fondant covered cakes. You can find me at thepinkbakerybox.com if you would like to elaborate more on this subject. I would love to share my experiences with you.
The Pink Bakery Box, Granbury, TX, http://ann816.wix.com/the-pink-bakery-box