It depends on how big you build it.
If it is big enough it can cost $10 million.
The limit on really huge rollercoasters is the need to attract a lot of people to ride on it. You can only build as big as you expect your market can sustain.
The tallest coaster in the world is kingda ka, and the price is mind-boggling: $25,000,000
I believe it was 30 million.
5 mil about plus maintenance
$12,000,000 USD .coaster-net.com/ridegallery.php?action=display&id=78
For the average rollercoaster, $15 million (US) and they are becoming more expensive.
£1
$23.58
14,000,000 dollars
$ 10
It may cost $ 5000 . 100000 , because they sometimes cost $ 700 . 1000 .
it cost 1p to build this building
Your whole life savings... im sorry):