It really depends on where you live. For example, in my area, a 1BR studio costs $1400/month, meaning ~$17k/year is going to rent alone. If you have kids, then you need more space, and 3BR apartments run $2k/month+ ($24k/year). After tax, that's pushing the 20-30-50 ratio (20% savings, 30% housing, 50% everything else).
My area isn't all that expensive either. If we look somewhere like San Francisco, triple those numbers (no, I'm not joking).
So yes, you can absolutely be cutting things close on $100k, depending on where you live. $100k in Mississippi would put you in the upper class, whereas $100k in SF would have you struggling for a lower-middleclass lifestyle. This site says $50k in Mississippi is comparable to $100k in SF. Here's an interesting article that compares income to be in the top 20% in each state (i.e. upper class):
- Mississippi - $113k
- Utah (my area) - $163k
- California - $196k