Generally they're worth whatever a collector wants to pay. In my experience average radars and repeaters in AU or better will bring about 10% over face value. However, only a subset of currency collectors are into fancy serial numbers and an abundantly large supply of these notes means lower prices. Anything under AU is unlikely to bring anything over face value. It's only when the number itself has a unique meaning can the prices go up. An example would be 66600666. Or perhaps someone's birth year, 19851985, or 10100101 (a true binary) would bring in slightly more. A star in the serial number would increase the note's premium as well. Certain fancy serial numbers can bring even higher premiums. Ladders, for instance can bring very big premiums (12345678). As can low serial numbers (00000008). Paired with a star in the serial number and high grade, you're looking at a nice cash out. My first note that got me into collecting was an ATM withdrawal on a 2004A $20, with S/N GF 00066600*. That sold for $100 on eBay. I attribute the high price due to the condition (gem uncriculated), the special serial number 666 and that it was a star note.
does anyone have a rough idea of what sort of premiums a binary high number note would fetch? its a Singapore $5 bill that's been folded in half but otherwise pretty decent a condition. my bill's numbered in the last 30000's.
