as you become more experienced you will be able to tell by feel the better quality cottons- and you can certainly find great deals on really good quality- you just have to learn to distinguish.
i've seen some pretty nasty cottons for $10 a yard---and i've seen some really good good quality cottons for only $5-so you can not just judge by price- you need to when ever you visit a fabric store- or quilt shop spend some time===touching- opening up a length from bolts and looking at it- feel it- feel the texture, the thickness- the even(ness) of the print- the absorption of the colors-
it can take years- or you may be fairly fast at learning what is (good)
and---
there have been many, many beautiful quilts made with wally world $2 a yard yukky fabrics----
and there have been many quilts that fell apart, ran, frayed- made from $12 a yard fabric from a quilt shop-
just spend time when you have the opportunity- and start---noticing.
don't just browse by color-and grab what is available- learn to (get up close and personal)