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.
Absolutely agree with this. And Bob's assertion that BB #28 is a great cover. I have always loved this cover, that (mostly) MA art is fabulous.
Great renditions of Green Lantern, Flash, Wonder Woman, Martian Manhunter and Aquaman
I say buy one if you can find one. (thumbs u