CAMBS, BARRA, £1000s but they were not dropped in the 100s like LOFAR, DIFAR, CODAR (waiting for the comments!) or HIDAR. Which were in the order of £150 a pop.
I suspect the route to improving medium size turbo props range and endurance is easier than reducing the cost of a large turbo fan.
Dagenham,
See earlier post on SEA HERC. A400 would probably be able to do the job. But it would probably end up costing the same to develop as a P8 would be to buy off the shelf.
I still wonder why HAAWC. Just thinking about a field of laying a field of 32 buoys. What would be the saving in terms of fuel burnt at lower levels balanced against the cost of HAAWC buoys.
I suspect aircraft performance or more likely unacceptable fatigue are what is driving HAAWC.