[amunicio]

Let's take your own reasoning and let's apply it and see where the numbers fall.

The Bart cost was $1.586 billion (according to Wikipedia) or around ~$10 billion of today's dollars.

Let say that back then we had put that money ($1.586 billion) into an annuity in perpetuity and given the money each years to the riders so they will find alternative means of transport.

So if instead of building bart back in the 70's we had put the money into a perpetual annuity, we would be receiving the sum of $63.5 millions a year from the annuity (your own numbers seem to indicate a 4% yield). That is less than 50 cents per ride (according to Wikipedia Bart gives 129 million rides a year).

I don't think the cost is insignificant compared with the level of economic activity that the 400.0000 daily riders generate for SF and the Bay Area in general.

And now imagine 20 years from now how much $63.5 millions a year will buy you compared with the benefits of mass transportation.

[rayiner]

For things like endowments, the general assumption is that you can get a 4% yield that keeps pace with inflation, without touching principal. So you'd be up to $300 million per year today. That's about $2.50 per BART ride of $750 per year per BART rider, which is a believable number.

The problem that you're ignoring, however, is that the relative cost of building infrastructure today is far higher than it was in the 1970s. If you built BART today, it wouldn't cost $10 billion in today's dollars. NYC's recent projects are running $1.5-3.5 billion per mile of subway track. BART has 28 such miles. That's $42-100 billion, not including the other 70 miles in the system.

So what if BART had cost $8 billion ($50 billion in today's dollars) instead of $1.586 ($10 billion)? Instead of having to great $2.50 of value per ride to justify the investment, you're up to at least $12.50. Or $3,750 per daily BART rider. Is each BART trip generating that much value compared to doing the same trip in a car?

[masonic]

  That is less than 50 cents per ride 

... if you ignore all the years' operational costs, personnel costs (including benefits and pensions), debt service, etc.... which is the lion's share of the costs.

[harryh]

Your math is wrong. You can (at least historically) get a 4% annuity that rises with inflation in perpetuity.

[amunicio]

Where can I get a save investment that pays a 4% annuity that rises with inflation?

I'm genuinely curious. My father is retired and has some savings and that would seem like the ideal investment for him.