Well I think you do have talent!! There's only two cakes there to judge you on...but I like them both and I would pay for them!
The easiest thing to do is to set a standard price to charge per slice/person. Don't just guess!
Add up the price of your ingredients, add in a small charge for buying/sourcing them (be it at the grocery store or a cake supply store), add in the price of your materials like cake boards/food colourings/gumpaste/decorations/cake boxes, add in a price you are willing to be paid for your time/labour/electricity...then see if you will make a profit.
DON'T SELL YOUR CAKES ON A LOSS...YOU WILL NOT WANT TO DO THIS AND PEOPLE WILL TAKE ADVANTAGE! (Anyone who hears you sold Mrs. Smith a big cake for $25 will expect the same. Don't start down that road of feeling "obliged".)
At first, you might barely break even, but the experience and the photographs of your work are worth the most to you...but later on, it can become the financial profit.
Hope that info helps you. It's an awesome, creative and artistic business. This website is certainly addictive and gives you tons of ideas! Keep posting for everyone's feedback too.