It's the first I hear of a Steady Betty. Went to google and saw a nice video on the "Betty" products. Has anyone used the hand strips for free motion or the ruler Betty strips?
About the quarter inch seam, Annie Pearl (love your name!) -- have you ever tried doing a scant quarter inch seam. I like to think of it as being just a thread width less than a quarter? On one of my machines, I can move the needle just a smidge and achieve a scant quarter seam. On the other I mark my presser foot with a tiny dot (use permanant Sharpie) so I can spot where to follow along for a tiny bit narrower seam. The thickness of your fabric has a lot to do with how it affects the size of your block once the seam is pressed. I'm sure there are other members who can better explain the process before you spend that kind of money for another gadget. Good luck