The Tomahawk missile program has been going on for decades, and has cost over $10 billion dollars — just for the development. This does not include the actual cost of the missiles themselves.
The cost of each Tomahawk missile varies, depending on the type of missile. More simple versions of the Tomahawk missiles cost $500,000. According to preliminary reports by Brian Williams of NBC News, it appears that the missiles used in the Syria attack cost around that much.
However, the Block IV versions of the Tomahawk missile, which are more complex and can hit moving targets, cost up to $1.5 million each.
The total cost of President Trump’s attack on Syria, then, is between $30 million and $100 million.
Only 23 US rockets hit their target – it is not clear where the 36 others landed