The life expectancy of people with similar living conditions to Amazon's high-paid employees is higher than average. The correct comparison is with people who have similar living conditions, except significantly lower stress levels, which is higher still.
Which is besides the point. Who works for Amazon for 30 years? Amazon hasn't been around for 30 years, and their turnover is high enough that I expect it'll be a while before they have any 30-year employees, excluding the owners. So Amazon workers probably wouldn't have a life expectancy as low as 50, regardless, even if working there did make your body degrade twice as fast.