Lock Boxes....Electric or Combo?

The question is which type of lock box do you use and why?  See I use the combo type since I supply them for the entire office and they are much less expensive at only $10 bucks each.  I like the idea and the additional safety from the supra electronic lockbox, but I can not justify spending over $100 for one lockbox.  Not to mention, that in my area, about 60-70% of the agents do not have the key to work the supra box and thus it limits our showings.  you would think that with all the realtors out there we could all band together and figure out a way to get the supra boxes for much less than the current price.  what are your thoughts?