You bring up an often overlooked point. The friction of switching tasks. Some people (non-technical managers especially) don't understand the price. They think

You bring up an often overlooked point. The friction of switching tasks. Some people (non-technical managers especially) don't understand the price. They think "oh, I'll just have them jump on this for 15 minutes, then that for half an hour, then the other until lunch". Wrong. You don't get 15 minutes + half an hour + whatever until lunch. You can take 30% + off the top for the switching. This holds true in non-technical fields as well. The ideal workday is doing just one or two things. That's where a person gets the most return on effort.