I think it matters whom you are buying from. If the FQ are of marginal quality, cut wonky, or minimal size, it's not a bargain at any price. KQ tends to cut generously, and I've never bought anything there that wasn't first quality. They will also take things back if you're not pleased. Also, it may matter why you are buying the FQ. If you're stash-building, it's worth something to have fabrics that someone has gone to the trouble of harmonizing for you. And if you're really into a matched set, there's always the FQ assortments or jelly rolls from a single fabric line.
I think, all in all, it's a great way to learn about fabrics and start a collection. Some of your FQ will have identification on the selvedges that will tell you what fabric it is, and you can use that to order yardage online. Watch for sales, too, as many companies have specials at times. You might also consider other types of collections. My first thirties reproductions were from a huge 10" square collection. It's a great way to have just a bit of a lot of things and to find out which ones really call to you.
Hugs,
Charlotte