It's not as if there were dozens of Concorde flights taking off spaced throughout the day. Two guys in a pickup truck could have driven the runway at 45mph and would have spotted the strip. International airports are teeming with spotters, many of whom would pay to go along on such a ride, so it's not cost.
If runway inspections were only carried out before Concorde take-offs, as I read into the above (?) wouldn't that infer that there was a potential problem with the Concorde on every take-off ? If so ..... a) would you want to fly in it or...... b) fix the problem !!
But then, fixing the problem would cost money, and presumably a weight penalty if under-wing strengthening was required, which of course leads to payload penalty, which comes back to money ....... !!
Not suggesting that AF or BA would ever let safety be second to financial considerations, of course.
