The ETF goes down, but so does the value of the phone - you're also paying off the difference in price every month.
On Tmobile when you bring your own device you can get a $50 everything plan - the equivalent plan is $100 on competing networks. Granted you could argue this isn't all subsidy and that Tmobile is also cheaper because their network is worse, but when you compare to international cell services this doesn't appear to be the case.
The cost of early termination + subsidized price is still quite a bit cheaper than the full price of the phone.