I have some actual "Dockers" brand fabrics here in my shop. When actually weighed out it comes to 13oz per fabric yard. (36" long X 60"wide)

This is the lightest Poly/Cotton I will use for one of my Contemporary Kilts.

I have purchased fabrics from sellers like the one you give the link to and their "Pant" weight fabric actually weigh 7-8oz on the same scale.

Please, please do your self a favor and buy the best, highest quality fabrics you can find. The difference in total cost of fabric only a $20.00 bill.

In the end you will have a Kilt you can be proud of.