This is all assuming you need a flagship $600 phone.
With very capable phones like the Aquos Crystal and Desire 510 coming to Sprint, the non subsidized plan model starts to make more sense.
ED1500 w/ 4 lines = $210 /month 4 Desire 510 = $0 on contract
24 Month cost = $5040
20gb family share pack w/ 4 lines = $160 /month 4 Desire 510 = $860 w/ tax
24 Month cost = $4700
It isn't a ton of money you are saving, and you do lose unlimited data, but for some people it will be the best option.
Also, if you can keep your phone for longer than 24 months, then the savings really start to show up.