This is strictly second hand info but I know someone who was told by a
non-destructive test engineer that, even if they approve some sort of
eddy current test, it would likely cost several thousand (I think the
number was "5" but I'm not sure) to do the test. The cost was
attributed to the type of machine necessary to do the test. From what
I understand, the location of potential cracks is buried deep inside
the wing and normal equipment can't do it. On top of that it would
likely be a recurring AD. This particular engineer, citing liability
concerns, said he wouldn't do the test even if he had the equipment
and could get the price. We were offered $5000 for ours before the AD
came out and we were a little insulted by the offer.