Don't know the TV spot, but looking at their site...
It's the trade-in savings that allows them to substantiate their claim.
It's easy to infer that they're the only source at all, but that's not technically what they're saying.
Not to poke fun at Verizon (I use them for my hotspot service), but I did get a laugh at how they're touting their having the highest peak speeds on their LTE-A network. Fastest theoretical speeds are nice and all, but the practicalityy of it is that people can't rely on peak speeds they'll likely never see except at 4am in remote areas... Fastest average speed is a much more appreciated stat.