Never bought a gun through gunbroker.
I also did a search and there are some 75B (various variants) available, but the 10 rounders are rare. Yeah, I could get them pinned/blocked, but another cost and hassle. Even then, the pricing isn't great. I got a pretty good deal on this order and it's not like I "need" it, so I am willing to wait. I too prefer to support and go through LGS when they can get what I want and the pricing is close. With shipping and FFL, the guns on gunbroker would come out a good amount more, like 10%+.
I have bought FFL items online before, but usually only after the LGSs can't get it.