One issue is that you may pay ten people 1MM annually to write your software, but the productivity distribution is likely not only non-equal but also non-linear

One issue is that you may pay ten people 1MM annually to write your software, but the productivity distribution is likely not only non-equal but also non-linearly so. Those at the top of the productivity distribution are the more likely to be able to find new employment, so you may be losing more than a tenth of your development output by going that route, and finding a replacement for that type of employee may be much more costly and difficult than average.