If he pays 2k a month and you pay 700 a month thats $24,000 vs $8400 a year. Given that 120k in the bay after tax is probably roughly 95-100k (guesstimate) the simple question is, is OP's after tax pay comparable to your pay relative to housing? No its not, he pays 2.8 times more rent than you. .8 of that is EXTRA because of where the location is (extra 6k a year). So given that plus OP's family expenses its actually fantastic hes saving 2k a month. That 'extra' $500 you 'could' save is what OP pays extra per month (that 6k/12) just for you to be able to say 'oh but thats the bay area'. To make my point more clear take that extra $500, add it to his take home pay. Great, now you are both making equal amounts compared to housing. OP saves 2.5k a month, you save 3k. Now, have yourself a family and try to save 3k with family expenses.

I think after adjusting for cost of living, you are making far more with your 70k salary than OP is with their 120k salary.