Corporate stores have less ability to offer deals. Indirect dealer will wheel and deal you better if you find the right rep. When I sold Verizon we used to give referral credits (which you are not supposed to do)and deep discounts on accessories for example. Those power chargers only cost around $5, so there is a lot room to wiggle if it is going to get you a sale on a contract.
I stopped doing it in 2007, but i don't think much has changed.