It seems like it matters a lot what they do with the test results. If they end up compiling some statistics about COVID prevalence, or if they binary-search positive results in the pool to narrow down which kids had COVID, those could be reasonable things that warrant the testing and might not cost much. If they end up quarantining the whole classroom for a week or two when the pool tests positive, then it cost a lot.
It seems like it matters a lot what they do with the test results. If they end up compiling some statistics about COVID prevalence, or if they binary-search positive results in the pool to narrow down which kids had COVID, those could be reasonable things that warrant the testing and might not cost much. If they end up quarantining the whole classroom for a week or two when the pool tests positive, then it cost a lot.