If you cut out the extra information, the sentence reads a lot more clearly.
Staying connected is what makes the cost seem well worth it to them.
Breaking it down a bit further into components:
X is the thing that makes Y true for Z.
In this case "X" is "staying connected", Y is "the cost seeming to be worth it", and Z is "them" (whoever that happens to be in the magazine article). So as you can see, staying connected and seem aren't a subject/verb pair. It's almost a cause and effect statement; you're basically saying "because X exists, Y happens (in relation to Z)."