People have had 10-year old plans. Remember that sending bits through the air is actually free, maintaining the network equipment costs money (and other customers would have paid for that already).
However, subsidizing a phone to the tune of $350 cost real money since that's paid to the OEM. Data does not cost as much as what Verizon charges you.
Now, if they let everyone have unlimited 4G, that would be a different story, but they've stopped offering those plans and of those people, few have enough money in their pocket to pay full cost for high end phones ($650+).