Sprint advertises unlimited everything for $69.99 per month and then adds $10 for "4G" devices, even when there is no service in the area. That's $79.99 + taxes and fees, no discounts for multiple lines. Assuming taxes, fees and surcharges like every carrier has, 8% or so of the bill, that's about $86.40 per line. You're saying you have 5 lines at $50 each, I have no reason to doubt that's your setup, but that's not what new customers get. My account is $84.60 per person including all the fees, etc, so about $2 less per month than it would be if I went to Sprint.
I wasn't being sarcastic; it sounds like it's a YMMV depending on when you set up the account, etc. but for my area, not only is Verizon the cheapest of the main carriers (only AT&T, Sprint and Verizon exist here), but it's also by far the best service.