San Francisco real estate has reached yet another crazy extreme.

The household income needed to buy a median-priced home in the city reached a new high and is now $303,000. That's according to the California Association of Realtors affordability index, which is based on sales in the fourth quarter of 2017.

The index approximates the percentage of households with the minimum income needed to buy an existing, median-priced single-family home with a 20 percent down payment at the current interest rate.

The new salary number is what a buyer needs to make to afford the $7,580 payment on a $1.5 million home, the fourth-quarter median.

A report from Paragon Real Estate that looks at the data points out, "The percentage of households who can afford to purchase a median priced house is 12 percent."

This number is certainly low, but it's not the low point. In the third quarter of 2007, an estimated 8 percent of people living in San Francisco could afford to buy a median priced home.

Patrick Carlisle, the chief market analyst at Paragon who worked on the report, says these latest figures are yet another example of how low housing affordability is perhaps the greatest economic and social issue facing the Bay Area.

"It impacts the ability of 'normal' working people to continue to live here and raise families here," says Carlisle. "It impacts the social and multicultural fabric of the region, the wellbeing of residents, and their intentions to stay or move. It affects businesses as they try to recruit new employees, who may be evaluating other options in other areas with much lower housing costs.

He adds: "Demand has been far outpacing supply. One can only hope that the situation will normalize with the construction of new housing, and of new affordable housing in particular."

It's important to keep in mind that this data doesn't incorporate changes to the federal tax code limiting the deductibility of mortgage interest and property taxes (and state income taxes).

Carlisle says, these changes will "will presumably have a further negative effect on affordability percentages in 2018."

What's more, interest rates started climbing slowly in the new year.