The city has to pay for the whole thing? Is no federal funding able to help? I would think that since the bridge is part of an interstate that the city doesn't have to fund everything on their own.
Of course, government at every level (especially the state of California) is broke. I see where you're coming from, maybe this is a project best left to a time when there is more funding available, but times like these are when suicides go up. I think the nets aren't going to save lives by catching people as much as they will deter such activity.
Another thing to consider is the cost of search and rescue. How much does it cost every time a person or body has to be pulled out of the Bay? How much does it cost to look for bodies? I honestly don't know the answer to that but it has to be costly to the city to deal with that, as well as the handling and burial of any John/Jane Does that might come their way. Also, I don't really see how a safety net is going to detract tourists. The way I've always imagined it, I never really thought it would take away from the beauty of the structure and scenery. Do you have any research to back this up? I definitely see your point about the cost, and certainly if there's no money for it I don't really understand how it can even happen, but a rescue net probably is a good idea that should have been done years ago.