While I have rented exhausting styro demo cakes... this blog post is right... There is no cost savings or time savings... Sadly I've encountered too many planners who have told their brides otherwise...
http://fayecahill.com.au/blog/the-styrofoam-lie/
Styrofoam Cakes
Here is some great advice for brides trying to decide on whether or not to do wedding favours!
http://www.brides.com/blogs/aisle-say/2016/03/wedding-favors-guests-dont-want.html?mbid=social_facebook
Wedding Favours