yeah it is heavy, I had similar thoughts. I actually purchased and returned a couple other lighter mounts. The other mounts mounted with screws and I couldn't use bolts because of the way the mount separated. In my case I was able to bolt it right through with fender washers and nylock nuts. I thought about even putting a backer board on it but I don't think that's necessary.
I actually emailed Adventurer and they told me the stock mount they use is 8lbs as well. I think it may even be that exact one.
I just really like the travel latch, I know it's way more money than a cheaper mount but the latch works quite well and I didn't want to have to mess around with coming up with another way to store the tv for travel.