The main thing being the styrofoam for the bottom three tiers of cake. Many weddings now have styrofoam cakes and then serve sheet cakes... its not any cheaper. The trick is because the foam is so firm, it can be challenging, however, I love it! It is also durable in case you drop it on the floor... but that would NEVER happen to me... ok I dropped the blue one right after I had covered it in fondant... boy was I mad... but luckily nothing happened to the styrofoam, the fondant just tore. So, I tore off the fondant, kneaded it again and rolled it out to about 2 feet in diameter, then covered it again.
It took about 40 hours to do the whole cake, working in the evening gradually... 5 hours at a time. But.... it was worth it, another cake to my portfolio.