hCOL is mostly housing-related. Over $300 per sq ft city median is high. Anything under $150 is low.
Isn't that kind of arbitrary? I guess I've always lived in LCOL! :D When I lived in Southern California, I paid $110 per sq ft in 2010. I sold five years later for $233 per sq ft.
Most recently, I paid a whopping $68 per sq ft for my 1 bedroom co-op apartment here in Scottsdale, AZ. :D That was obviously a huge motivation for moving here, but just because I found an awesome deal on housing, doesn't necessarily mean it's a rock bottom cost of living across the board.
My impression is that the restaurants and take out food places are more expensive than Southern California was. For example, 5 street tacos will cost me $7-$8 instead of the $5 they cost in CA. Lean Cuisines at Kroger-owed Frys cost $2.79 each instead of the $1 the same lean cuisines had cost at Kroger-owned Ralphs. Auto and property insurance via USAA is more expensive here than it was in California as well. Of course, electricity rates and gasoline is a lot cheaper....does the cheaper housing make up for everything else? Over a multi-decade span, probably. But I guess it depends on your lifestyle.