California progressives’ single-payer health care fever dream is back. This time, the cost could hit half a trillion dollars a year.  Single-payer means the government pays, for everything. Several candidates for governor are promising just such a government takeover of the state’s health insurance system. Billionaire Tom Steyer says, “Bernie Sanders was right. We need single-payer health care.” His campaign ads place a single-payer system at the center of his agenda. Betty Yee, Xavier Becerra ,