Prime all together only made 14 billion. Considering that prime almost assuredly doesn't cover its 2day shipping we can be very sure, the video unit is _certainly_ not positive.
What's even more important is this quote from Bezos, which directly states it's their strategy:
"We get to monetize [our subscription video] in a very unusual way," Bezos said. "When we win a Golden Globe, it helps us sell more shoes. And it does that in a very direct way. Because if you look at Prime members, they buy more on Amazon than non-Prime members, and one of the reasons they do that is once they pay their annual fee, they're looking around to see, 'How can I get more value out of the program?' And so they look across more categories — they shop more. A lot of their behaviors change in ways that are very attractive to us as a business. And the customers utilize more of our services"
https://www.businessinsider.com/amazon-ceo-jeff-bezos-said-s...
It's a _publically stated strategy_.