If you had to choose, would you rather spend money on overdyed floss or hand-dyed fabric?
I'd spend it on fibers rather than fabric. Because you can use the fiber on more than one project, but the fabric is just one project.
For example: I found 22 of 25 fibers I needed for my Color Tiles canvas piece that I was kitting up with my own choices rather than what was called for. Left that store thinking I'd need to go to another store on another day to find the final three silks. But I wisely checked in my stash and found three that suit this project beautifully. Two of three are partially used skeins. I love when this happens.