jac, what do u mean by mini? i only ever make to 52mm large cupcake/muffin size.
just weigh out your ingredients from new packs.....see how much you have used...roughly 1/4 of a pack, 1/2 a pack etc see how much youve paid for your ingredients and work out the right amount of money
say youve paid 50p for a pack of sugar, and youve used half a bag...thats 25p
then do the same for your buttercream and decoration, box etc.
then dont forget to include electric/gas for the oven, and people forget to take some for the petrol youve used getting your stuff, etc. and obviously your time for doing it, coz sometimes they take longer than planned!
im seriously thinking about charging more for the time i spend cleaning my kitchen afterwards
people forget all the little things to add on which could bring you out at a loss, like the boxes, any decor for the box, the cases of course! (i just forgot that LOL)