The problem I'm seeing with this though, is when you upgrade they lock you in for another 2 years. So you're stuck in an endless loop paying the high subsidy prices, even if something else better comes along
I think, first off, you have to understand that the ultra-vast majority of population doesn't care. Those of us "smart enough to know" then typically have specific reasons for choosing Verizon and don't mind signing the two-year contract. There's two ways of looking at that cost.
Buy your phone outright. Spend $600 on your phone (a "cheap" one) and have the right to leave whenever you want.
Buy your phone on contract. Spend anywhere from 0-300. Let's split it and say $150 which is the going price for most new flagship phones after a few months of release. Have an ETF of $375. It goes down $10 every months. Nine months later, you want to Sprint (just for the sake of the argument), now you've paid $435 total. And that amount goes down $10/mo. Even if you tack another $150 on top of that for like a Note 3, the amount goes to $615. Still cheaper than purchasing a Note 3 outright.
If you know you're going to be with Verizon for even 4 months, you still come out ahead getting the device with a subsidy.