While I think it's probably part of the reason, if it was the only reason there are bound to be other less customer hostile ways of solving that particular problem.
This seems consumer-hostile because the entire thing is consumer-hostile - they want ML researchers to pay more for graphics cards because they have more money to spend, not because they can offer superior performance. (They can offer superior performance to GeForce, just not superior performance/$ or performance/W.)
For a very large number of problems that are smaller than both or bigger than both, that extra memory bandwidth is a lot smaller than the price difference.