Okay, but why are wedding cakes so expensive if they're only flour, water, eggs and butter, then?
Because that wouldn't be a wedding cake, it would be this:
Now, I assume that a DIY-caker isn't thinking of this as being the result when they decide to take the task of making the cake on themselves in order to save money. However, you do have to buy the ingredients as the first step in your DIY cake adventure. Then you need pans, cake boards, dowels, and let me add in the cost of electricity, water, and gas to drive to the store for the shopping. Then the cost of your time, because when you're working on the cake you're not able to do other things.
After taking all of this into account, I'd argue that wedding cakes really aren't that expensive, but some people will still try to make their own cake in order to save a little. (But remember that on average, wedding cakes are only about 1.7% of the total budget. Just saying...)
Well, okay then. You're going to do your own wedding cake. Will you just do it the first time without a practice run? Probably not, so we need to add in the cost of a practice cake or two, and boards so that you can practice stacking the tiers. So even before you start baking the cake, you've already invested time and money into that cake, for shopping and ingredients.
And how many ingredients do you actually have to buy to make a three-tiered cake to serve between 100-120 guests? It'll probably take a while to figure that out if you've never done it before.
I added up the cost of everything you'd need to make and deliver a three-tiered cake and a two-tiered practice cake, including groceries, pans, boards, boxes, and other equipment. I was shocked myself, but the total was around $175 for everything. And that's not even including items to decorate the cake. If you wanted flowers on it, whether sugar or fresh, you'll drive the price up closer to $200.
(I used a scratch yellow cake with plain vanilla buttercream as the basis for this exercise...If you wanted something fancier the price of ingredients would probably go up. Even if you used a doctored cake mix, the price will be right up there in that neighborhood.)
This is assuming that you have nothing on hand as far as pans and equipment go, but why would you if you've never had to make odd-sized cakes before? And yes, you could buy everything using coupons and on sale from Ebay, but then you have to add in more time for bargain-shopping. It's a trade-off in terms of whether you're investing time or money.
This is also assuming that nothing goes wrong, and that you only have to do one practice run. It also assumes that you don't sign up for a cake decorating class, which will be at least another $100 or so by the time you get to the tiered cakes section, even before you buy the materials.
So you'll end up putting close to $200 into a cake, conservatively. It may not seem to be so much because you'll be shopping for things bit by bit, but it all adds up. I also didn't add in your gas to go shopping or any utilities. Or the shipping fees you'll pay if you end up having to buy things online.
So based on my pricing of around $350 with delivery for a cake this size, you've saved $150 on the cake, as long as you didn't take a class, you only went shopping once, and don't want a flavor other than something basic.