By far the biggest cost to software companies is employee turnover because the second greatest cost is employee education and training. We've measured developer productivity in multiple ways and time to full productivity within any new team/project generally is 3-6 months. Average empployment time at any single company in the tech industry is now 18-24 months. It makes more sense to pay 3-4x for most work, rather than have to deal with HR, education, and retention overhead.