For me, I think of "a lot" of fabric based on yardage, not based on amount spent. I found a bunch of fabrics at a thrift shop once, mostly 8 yd by 60" wide pieces of cotton apparel/lightweight home decor fabric that I bought mountains of to use for quilt backings. It was really inexpensive and I paid hardly anything, but considering the plastic bag I carried it out in nearly cut through my fingers from the weight, I say it was a "lot"! (I bought about 40 yards and still have about half of it!)
I also went a little crazy on my last trip to Hawaii...fabric prices are really very reasonable there, and I brought home 30 yards of various Hawaiian prints.
By contrast, if I pay a premium price and walk out with hardly any fabric, I don't feel like I 'bought a lot of fabric', I just feel like I spent a bunch of money.