Karen’s Cakes and Bake has quoted a piece of advice I’ve heard. As an easy rule of thumb, you would charge 3-4 times the cost. Sometimes, I have had to figure in 4 times the cost of ingredients and the cost of labor. Kitchen/ cutting cakes are exactly as stated above. Of course, it won’t take you as long to decorate 2 sheet cakes as it takes to decorate and cover a tiered cake with fondant.
The cake you have shown also has gumpaste flowers on it. Some bakers charge so much per blossom. Something else you need to keep in mind is that different areas can charge differently. For instance: I am located on an island. Any specialty sugar craft item I need has to be ordered online. The closest Walmart is an hour and a half away and the closest Michael’s Craft Store (for cake decorating supplies) is 2 1/2 hours away. I charge a premium for a premium service, in a very touristy beach location. My prices might be a little bit different if I lived closer to a city where supplies were readily available.
Be sure you don’t under cut yourself. You will start to resent your customers. Make sure you are paid what you are worth!
Good Luck!
Psalm 127:1 Unless the LORD builds the house, the builders labor in vain.