Oh Jackie I'm sorry to hear that this unfortunate experience has led you to make the decision to no longer make cakes. I pray that in time these bad feelings will fade and that once again you will want to sell your cakes.
When I first read your opening post my reaction was "these people are trying to get away with something by shortchanging her", but, after reading through and thinking about it more I've changed my mind.
Seeing that you had always donated cakes in the past to the church and there was no price quote or contract prior to consumption of the cake, I now think that they were just shocked with the price. Having never paid before, they assumed it was going to be "warehouse pricing".
Saying that though, I still believe the daughter handled an akward situation incorrectly.....and now in turn this has led to your hurt feelings and you giving up something that you are obviously passionate about.
I think if they knew how you are feeling right now they would feel horrible and offer to pay you the balance. By not being honest with them, they don't have the chance to correct the situation. I urge you to give them the opportunity to make this right, so that you can have a clear heart and return to the church.
Than if you receive a request for another cake you can say that with the rising cost of ingredients and utilities, you regret that you can no longer donate your cakes. But, you will be happy to "sell" them one at a "pre agreed and contracted" price.