As artbrooks noted, health insurance is not free to the legislators. I don't know what the amount paid boils down to- perhaps $100 - $750 is correct. However:

"Members of Congress are under the Federal Employees Health Benefits Plan, the same menu of health insurance and managed-care options offered to federal civilian employees.
Also, like federal civilian workers and retirees, lawmakers who elect to participate in FEHBP pay premiums which, by law, must be set to cover 28 percent of health benefit costs.
http://www.military.com/forums/0,15240,84168,00.html

Let's see. If my health insurance costs $400 per month (a conservative figure) and I only need to pay 28%, that means I am less than $250 out of pocket. Yep, I can do that.