I personally think it is a needless expense. People will know that they are going to on their feet and/or dancing the majority of the night and if they don't wear the appropriate shoes then that was their choice. I have always just gone barefoot at the end of the evening if my feet hurt.
My suggestion if you're on a tight budget or trying to keep the budget as low as possible then forget it! It's an unnecessary cost that likely won't get used. 9/10 times the ladies will ditch the flip-flops or other provided shoes to go barefoot anyway. I was considering it but then I realized that it will probably be money poorly spent. Our dancefloor is no drinks allowed so no worries of spills or broken glass.
Personally I'm leaning towards cutting it out - while I think they're cute, it's likely a spot I can save $50-60. Plus our venue has a nice slate tile floor and no bottles allowed so I can foresee a lot of barefoot dancing.