With cakes you have several options-
Make it yourself,
Buy from a supermarket or cheap commercial bakery,
Your best friend’s dog’s auntie’s neighbour,
Someone half decent who earns nothing from it/makes a loss,
Someone good who charges a lot but can cover their costs and a bit of their time.
Someone good who charges a fortune and can make a living.
So it depends on your budget, your standards and your ethics. People have NO IDEA how much expense goes into cake making. I made an 8” round cake recently. For the board, box, ribbon, cake dummy (to be the small ‘cake’ on the top) and the icing it was about £35-£40. That’s not any of the actual cake ingredients or even the chocolate and cream for the ganache, the colours or the time to make it! That cake was probably about 10-15 hours of work (I don’t add it up, it’d be depressing) and it was a 1.5 hour round trip to deliver it. Now think about how much I’d have to charge to turn a profit.
Yes people can and do charge cheaper, but please don’t complain when the quotes seem expensive, see how much this stuff actually costs and you might understand it a bit better.
And I use margarine for sponge cake too, it’s better!