I assume $5 billion would be conventional diesel commuter rail with a max speed of 79 mph. And the $15 billion estimate would be for high speed electric commuter rail simular to Amtraks northeast corridors Accela trains which have a max speed of 150 mph.

Here's the thing, spend less and it will be a waste. 79 mph diesel trains running 2-4 times a day won't be popular. Even though it only costs $5 billion from Pueblo to Fort Collins which isn't bad on a cost per mile basis, it 2ill be too slow and not frequent enough to attract riders; making it a waste.

Of you spend $15 billion and get 150 mph train a that run 12 times a day, then you have something faster than driving and frequent enough you can easily integrate it into your schedule. The ridership would be much higher; thus making it more viable and worth the investment.

So I must warn either do high speed rail, or don't do it at all. Anything less than high speed rail will be a waste of money.