That 50 people team probably costs at least 250000/month. Are you going to take away a tool that everyone on the team needs to save 1250?

Or put another way, how much time would you need to replicate what Docker offers for a team of 50 people? If it takes more than 25% of the time of a single employee, then Docker is cheaper (assuming your employee costs $5000 a month, which I guess is a lower bound for an engineer).