You've got that exactly backwards. The profit motive being predictable is what every market based economy heavily counts on. Which is to say, most of the world's economic activity relies upon the profit motive as the foundation of trust.

Hundreds of trillions in global wealth and $100 trillion in annual economic output are powered by very predictable self-interest. You can build trust networks around it and you can build regulations based on it, precisely because it's extraordinarily predictable and universal to the extent necessary for the whole system to function with billions of participants.

I think you're both partially right. Profit motive is what drives people, but profit margins will be shrunk so in an established mining ecosystem like bitcoin you probably aren't going to make any profit (after accounting for opportunity costs).