This is the equivalent to buying a house or car with cash to save on interest. Of course you save money by paying full-price up front instead of financing. It only works if you have that much cash available though.
Consumers have forgotten.
A) Your expenses shouldn't exceed your income.
B) You should carefully evaluate the price you pay for financing.
There is nothing wrong with amortizing an expense, provided it doesn't break your income/expense ratio and you aren't overpaying on the financing.
Ultimately the best way to minimize your costs is retaining the ability to say "sod off, I'm going to [competitor]".
My point is that it's still not a "common sense" evaluation. It's a nuanced decision that must consider all variables.
To be completely accurate - Nexus phones are an exception. Even the manufacturer of Nexus phones sells their non Google branded Nexus equivalent models at significantly higher cost. There is nothing else in the market priced like a Nexus phone (probably because no one can sell these devices at cost because they don't have the cushion of massive ad revenues).