Health insurance costs vary dramatically. My wife and I have bought our own insurance in CO, CA, and OR. We usually pay around $150-250 / month (for us both, not each) for a decent plan with a deductible of $2k-5k. I always use esurance.com.
That said, he's in the worst insurance market in the US: NYC. To get the equivalent of the $168 / month plan we have now, esurance was at least $800-1200. Sickening. Best bet I found is Freelancers Union. Health insurance is horribly broken in NYC.
I'm also a consultant, and use Kaiser in California. I'm paying about $160 a month for full coverage. Although my plan does have a $2000 deductible, preventive care is free, so other than my premiums I haven't had to cough up anything yet.
I got a lot of questions about this so I added a paragraph which hopefully helps to address it:
"Healthcare is a big and challenging topic, so if you find this to a problematic point for you, there’s a whole chapter devoted to it in the all-around very thorough book Working for Yourself. The short version is that if you can get on your spouse’s plan, that’s a great option, and COBRA can also be used if affordable, and can be turned into a personal plan after 18 months. I decided to go with an individual plan, looking extensively at both freelancersunion.org and ehealthinsurance.com before choosing a plan from the latter."