I think it probably depends, in part, on whether that starting point was "typical" for a guy or not. (Also obviously there are cis women with big breasts and small areolae, cis women with small breasts and huge areolae, and everything in between...)
It's funny, because I was just recently looking back at the pictures I took for the first 2 years on HRT. I had tiny areolae to start with, even though I had visible gynecomastia with actual breast tissue; I'd say they were maybe a half inch across when I went on HRT. At the end of 18 months, they were at most twice that size. Then I stopped paying attention... and when I compared just now, at coming up on 6 years HRT, they're probably 2" across or 4x the starting size. They've also turned darker and pinker in color, and the nipples are noticeably larger as well. Still, again, if you're reasonably large to start with you may have a much less dramatic change, since that seems to be the rule with HRT - the farther from the female norm a given feature is, the more drastically estrogen can change it.