I think it`s relatively easy, actually.
I think B&B 29 & 30, Showcase 8, 13, 14, 17 & 22 are harder.
Just for sh*ts and giggles: link us up some of the easy to find B&B 28s in higher grade. I know there's an 8 out there.....and some 6-7s. But they are all few and far between. Try to compare that to the voluminous list of higher grade Avengers 1s. I'll have to respectfully disagree that it's easy to find a bunch of high grade B&B 28s.
RELATIVELY easy.
It`s all relative. I would say that more B&B 28s in 9.0 and above have come up for sale in the last 10 years much more often than the other books I`ve listed, except for Showcase 22 and that`s a recent phenomenon.
Also, my comment about being relatively easy was in relation to DCs. Marvels are a different planet. There`s no such thing as a scarce SA Marvel, particularly one as late as Avengers 1.
I agree with tth2 on all points, plus I'd add Showcase 23 - 29 and Brave & the Bold 31-33 to the list of comics from the same time period that are tougher to find than Brave & the Bold 28.
(thumbs u