Compare refurbished and new products on price and lifespan.
The refurbished discount only matters relative to how long the item lasts. Dividing price by expected life converts both options into cost per year of use, which is the comparable figure — a 30% discount on something that lasts 40% less is a worse deal. Shorter warranties are the usual reason refurbished lifespans are estimated lower.
Cost per year of use
Cost per year = price / expected life in years; compare refurbished against new on that basis
No. Manufacturer-refurbished units are tested, repaired and warrantied, which is why they command more than a private used sale and justify a longer assumed life.
Twelve months is common from manufacturers and reputable resellers. A 90-day warranty is a signal to lower the expected life you enter here.
Then the cheaper price simply wins, and the up-front saving is the whole benefit.