So much this (regardless of which carrier you want to use). I mean, if you have the money to burn, more power to you, I'm not telling anyone how to spend their money if they have the cash flow to do so - but to me its nuts paying even $500+ for a brand new phone.
I've been in the mode for the past ~2 years of buying used or refurbished immediately-prior gen phones (at the time I initially buy them) at a significant discount, say $250 if not less. This is also while dropping protection plan payments entirely through Sprint, and instead putting that ~$10-15 a month per phone into a Cap One 360 savings account and letting it build up over time.
If by some chance a phone were to suddenly die on me (have yet to have that happen - I did have to get an immediate replacement once on the very front end easily within the return period, but nothing where I'd used it for months/a year or two and then it died), I already have more than enough saved to go the same route again (we also have at least 1-2 backup phones, LG G5's currently, that we can fall back on in the interim where we just went ahead and upgraded using the same funds).
I've been completely satisfied using this approach for the past few years - both in terms of phone capability as well as the additional money in my account over each year that I'm no longer giving up.