The BCUSA tarp is 1.9 oz ripstop with a urethane coating. It is a very well made tarp. Of course, there are a lot of similar tarps that are just as good. Here is a similar size/weight/materials but only $50. Campmor
It isn't camo like the BCUSA, so you might want that camo feature for more $$. Part of the reason BCUSA tarps are more is because they are using the proceeds to fund the forum.
Here is the BCUSA tarp OM. BCUSA tarp

As for the rest of them, I would first look at the Campmor tarps and then compare prices. If the other ones are cheaper, then I would wonder why. I would also look at raw material costs. If the raw material would cost more than the finished tarp, I would also wonder why. Just something to think about.