Earlier quoted context omitted.
Service plans have really gotten cheap over time. Google Fi is like 24 bucks a month, and they're not even the cheap plan anymore.
That kind of proves the point though even at 24 a month if you have the phone for 2 years then the plan was $576 while the phone was only 350. The phone would come out to $14 a month. Do you value your phone as worth less to you than Netflix?
it depends on how long you want to keep the phone for. I bought my phone in 2017 ago for £400 and I pay £8 a month to a carrier to get an allowance of data + calls every month (not a contract, I'm free to cancel any time) so it's worked out at about £18 a month if you amortise the initial outlay.
obviously contracts are more expensive, and can sometimes, albeit rarely, be cheaper, you just need to do the maths.
the bigger advantage to buying a phone outright is you're free to switch network/carrier as the phones are unlocked, at least in the UK anyway.