odditory: that is exactly what large storage vendors do, purchasing drives (with a minimum AFR guarantee) and servicing the warranties themselves versus letting Seagate, Western Digital, Hitachi, Toshiba, Samsung, and the SSD guys service them.
What makes it slightly better is that drive prices tend to fall drastically over time, so if you purchase 20x $200 drives with warranty, versus 20x $180 drives without warranty, the drives that fail late in year 1, and also in years 2 and 3 will likely cost less than $180 to procure. Case and point, 2TB Hitachi drives fell in price by well over 30% from this time last year and 1.5TB drives were expensive 18 months ago but are dirt cheap now.