Again, articles that were written by someone with no clue about "cake reality," and who's obviously just parroting someone else's information without checking it out first.
There are a few points to remember if getting a sheet cake is something that you're considering, each of them things that I've actually run into myself (not just heard about or made up, what a concept!) when brides have ordered, or asked about ordering, sheet cakes.
First, this isn't always a money-saver. Let's say that you're planning on having about 150 guests. The general rule is that you need about 80% of the number of guests attending, NOT invited, for the number of cake servings. Not everyone has cake, for whatever reason, so 80% is generally enough. So the 150 guest count would need about 120 servings of cake. That would be a 4-tiered cake, but if you're trying to cut costs with a sheet you could reduce that to 3 tiers and do a sheet to serve about 48.
Well, if you get the cake from me, that will only save you about $25. I don't reduce my prices that much for sheets vs. wedding cakes. (See my previous post about wedding magazine articles.) For that $25 saved, you've reduced the height and the visual impact of your wedding cake. Not worth it to me, personally.
In general, for guest counts under 200 or so (and that's guests attending, not guests who are invited) getting a sheet cake isn't going to save a substantial amount of money. Unless you buy a really nasty sheet cake from somewhere that charges 50 cents a serving, and serve the good wedding cake to the rest of your guests. Nah, nobody will notice the difference...
Not to mention that your guests will find it kind of strange that you have such a small cake to feed so many people.
Okay, so let's say that you have over 200 guests. Having a sheet cake and a 4-tiered wedding cake will save you a little money, but let me warn you about the situations that I've encountered when delivering this type of cake setup.
Keep in mind that working kitchens generally don't have a lot of extra space to store extraneous food, so they'll often put the sheet cakes in the fridge to store them until they're cut. If they don't do that, they'll probably leave it on a counter somewhere in the kitchen
If the sheets are put into the cooler at the reception site, then served cold, the cake will seem stale. Cold cake isn't soft, and feels dry in your mouth.
If the cake is cut early, plated and left to sit while the serving staff waits for the wedding cake to be cut, the sheet cake pieces will dry out. The guests who are served the sheet cake will get dry cake.
If the sheets are left in the kitchen, where the food is being prepared, they can absorb the odors from the cooking food. The guests who get the sheet cake will have a flavor of fish/chicken/garlic etc in the cake. Yummy!
If the reception venue has no clue, (and this really did happen before) they could put the sheet cake out on a table to let guests cut themselves pieces. Not only will this not give you the serving numbers that you want, it's a little weird to expect your guests to serve themselves. Plus, who wants to look at an undecorated sheet cake sitting on a table during the reception? Even worse, they could put the undecorated sheet on the same table as the wedding cake! I once had to tell a guy at a reception site not to do that as he was unpacking the sheet and getting ready to sit it on the wedding cake table.
So if you do decide that having a sheet cake will be a good idea for your reception, make sure that you have someone watch to see that the caterers don't cut the sheet ahead of time, put it in the fridge, or let it sit out where it can absorb food smells. Or you can just get a wedding cake that will serve everyone, and not have to worry about your guests getting piece of cold, dried-out fish-flavored cake.