It will have cost exactly as much as it might have cost to perform any complex investigation.
Far, far less, you might like to consider than the trial, multiple investigations and eventual quashing of the convictions of the Guilford four.
I could cite many other cases...
In my view it's money well spent. We are a society who want, go after and do our best (whatever the cost) to discover the complete truth. This, I think is worthwhile.
I certainly want to know whether the SAS are implicated in the death of a princess (or a bus driver). I want to know if state sponsored executions are taking place and I want to know whether or not my government is complicit in murder as a one off or as a routine venture.
Don't you ???