No need to appologise
Last year before last when I imported some Idolomantis ootheca, 7 out of the 10 I got hatched. Hence, I bought some more. The one ootheca I cut open had living larvae in - could have been the only one, could have been one of many. We will soon see if the ones I kept, hatch. People realise the risks of buying wild caught ootheca, as I realised the risks of buying them myself.
As for your calculations, you do raise an interesting point. And depending on the results from these ootheca, will certainly depend on whether I buy any more of these again. However, as I said, I bought this lot based on the good results I had last time from WC ootheca.