Sometimes sharing sucks. Three people using one floor monitor, each asking for a bump in something different until the muddled sound emanating is more felt than heard. That's not the way to go. In-ear monitors let everyone adjust their mix to their own liking. Some want a simple mix. Some want a wash of everything on stage. That's what's great about in-ear monitors. You can give everyone what they need.
If in-ear monitors seem like an expensive way to go, compare it to the number of amplifiers and floor wedges you're going to need. You can actually get people their own personal mix through in-ear monitors for considerably less than a comparable floor monitor setup.
All prices are in USD.