Cost of living much?
No word on if regional cost of living was factored in. $100k a year in San Francisco will get you a broom closet you share with 8 other smug hipsters, or if you live in BFE $100k would have you living like a king in a gold plated double wide trailer. Also costs of utilities vary greatly across regions, not to mention continents/hemispheres.
So while DevOps engineers make more, due to their location they could be living in a van down by the river, and be upside down on their payments for the van.