I think it's a more a question of "all things being equal, why would someone pay $500+ instead of choosing the free option". You could argue for or against the

I think it's a more a question of "all things being equal, why would someone pay $500+ instead of choosing the free option". You could argue for or against the technical merits of the FOSS model (security, multi vendor support, modularity, extensibility, etc.) but those are minor. Its biggest selling point is that it's free. That's why all the other paid server software of the 90s and 2000s died out too. LEMP is good enough.