How much will using margarine instead of butter in a ratch cake recipe change the flavor/texture. I'll be honest. The cost of butter is killing me. In a rural area and at food lion it is 3.59 a pound as opposed to .79 for margarine.
Butter makes them lighter, taller, a finer crumb and has more flavor. Margarine has more water in it and is made with hydrogenated oils, so the cake won't be as tall.
Margarine will work, you will just need to experiment with a few recipes to see what adjustments will need to be made to make your cakes the height and flavor that you want.
There is nothing wrong with using margarine. Many bakers do it. Don't feel guilty if you have to go this route.
If you do want to stick with butter, see if you can find a place where you can order butter in bulk. It can be frozen and many times is much cheaper than from the store. Sometimes restaurant/bakery supply companies will allow you to buy small quantity of things. You will just have to go to them instead of having it delivered as a regular bakery would.
Why not raise your prices to accomodate the good stuff?
I typically use butter, but another cake decorating friend of mine actually prefers baking with margarine! We were just discussing this last night, because I was at her house while she was baking and was surprised when she pulled out margarine. Her mom always used it when she was growing up, and she likes the taste better. It will affect the flavor, though - just try both, and see what you like!