Opex won't be zero, but I don't think it'll be anything like HSR (or an aircraft). $20 seems too cheap. But I don't think $50 is out of the question at all if (and, agreed, big 'if') the capex costs are close to target.
Something else to consider though - those prices are for ridership levels that you could expect by connecting SF and LA. If you start to link up more points (Vegas, San Diego) the utilization of ALL the lines increases, which means you're amortizing the capex over more passengers... which helps a lot given the small fraction Opex will constitute.
To your second point, are you sure it'll be prohibitively expensive to integrate it into the city transit systems? As an elevated system I don't think it'll necessarily cost that much. I suspect it was omitted as much because it'd be expensive in concept evaluation time to sort the details of the integration as because they're just crazy expensive. Is it really that hard to get 2 x 3m tubes on stilts with a foundation every 30m out of a city? It's a very different proposition to putting in a new ground level rail line.
Something else to consider though - those prices are for ridership levels that you could expect by connecting SF and LA. If you start to link up more points (Vegas, San Diego) the utilization of ALL the lines increases, which means you're amortizing the capex over more passengers... which helps a lot given the small fraction Opex will constitute.
To your second point, are you sure it'll be prohibitively expensive to integrate it into the city transit systems? As an elevated system I don't think it'll necessarily cost that much. I suspect it was omitted as much because it'd be expensive in concept evaluation time to sort the details of the integration as because they're just crazy expensive. Is it really that hard to get 2 x 3m tubes on stilts with a foundation every 30m out of a city? It's a very different proposition to putting in a new ground level rail line.