The bullshit is hidden in the word "directly". You can define this word to mean whatever you'd like to mean. You can say a salesperson directly adds revenue to the company, but it's not really directly, the billing department is much closer to the actual money. You allow yourself to take the billing department for granted, but that's just because you don't work for the billing department. In the same way you could view the developers as the profit center, and take the sales department for granted.

I'll say it again, I'll be happy to see an objective definition of profit centers and cost centers.