This does seem to be a staggeringly large increase for what are mostly small incremental improvements (at best) in the benefits.
I was worried the instant I saw a large booklet enclosed with the letter from Amex. In my experience, the more they have to blind you with glossy brochures, the worse the actual news is. Turns out I was correct.
From Amex's point of view, they are taking a gamble that people will whinge about the price increase, but in the end will mostly suck it up and pay it to continue with the benefits. If this largely works, it simply means that $900 was actually too small a fee.
It's the large size of the increase in one hit that surprises me. I don't like it of course, and I suspect I'll be one of the people who suck it up and pay the fee. But I think I'll give it a bit more thought this year.