Cost of tools is added to the COGS, I treat it like ingredients, and a % of overhead that I apply to every cake, so yes, at the end of the day I pocket more for a cake than $15.00 per hour labor cost. But like every trade you pay for the level of skill. And yes, If I decorated cakes like some of the finest work I see on here perhaps I could charge more per hour, I'm just not that skilled, I am a beginner. I just started this a year ago. But I've asked very talented, high skilled decoraters what they pay themselves, everyone seems to go mum.
Last point. Every skilled trade profession has a barrier to entry. For decorators it doesn't seem like that barrier is to high, so the premium factor on that is slight, in fact entry to the field is quite easy. There are lots of ways to learn to decorate cakes and acquire the tools. There are lots of people that decorate cakes for fun. Moms make their own birthday cakes. All that factors into the market value of a cake whether or not it is fair or right. I don't think it is ever going to be a high paying profession for most. You can charge more because of your branding, very unique or rare product, scarcity of product, or a very special decorating skill but other than that ,what is the justification for charging more per hour than someone that has been decorating cakes in the grocery store for 20 years.
Yes my cake prices are more than $15.00 because my tool prices, overhead per order, time I put into a custom cakes, ingredients are more, but not so much my labor costs.
And perhaps I'm overly anal about costing because that was my job in a previous life. I have costs for everything. I understand I am the owner, and a certain percentage of my time is spent being an owner. I pay myself $45.00 per hour for that (also goes to overhead). Sometimes I'm just a baker and when I bake, I cost that out at $10.50 per hour. When I decorate it's $15.00 per hour. When I clean it's minimum wage. I have a price for shopping and purchasing/billing/accounting too. All this to ensure I'm profitable and if one day I so happen to need to grow I've already costed that into the equation.