The reason they put all the price in the shippng is to discourage returns. You can't recover shipping cost in a return. Racks (due to size) are not cheap to ship. Thus, no one would return a $6 rack if its junk, which the OP-linked rack may very well be.

I've bought 4 times from Abaxo and got some good parts at fair price, shipped super fast (you do get your moneys worth on the high shipping charge).

I think I'd pass on that rack though.

Nashbar usually has 2-3 decent cheap rear racks:

http://www.nashbar.com/bikes/SubCate..._202334_202379