First off, welcome to the forum!!! This is a great community with lots of knowledgeable and helpful people! You will no doubt find lots of inspiration and information here!
Your characters are wonderful...I'd say you've got a real knack for it! But the cake is tiny...Usually, prices are based on how many people a cake needs to serve. This looks like a 1 layer 6 inch cake? Not going to feed many lol
Do some research on cake shops in your community to get an idea what your base price should be. Then you add in your characters, fondant, anything above and beyond butter cream...Then there's' usually a stacking fee when you are doing a multi tier cake. Lots of variables,,,but the most important thing is to research prices, and try not to charge so low you end up under cutting the cake industry in your community.
Hope this helps :)