No one has found a way to make convincing one dollar bills for less than a dollar.

Heck washing dollar bills is a way to get base paper for higher denominations. (one of the incentives for moving away from consistently colored currency)

Which was the premise of the first Jack Reacher novel.

..or to moving towards $1 coins.

But what about old $20 bills. Strange I cannot find a list. Kinda worried.

If you're relying on this one feature to detect counterfeits, that's a bad approach. Magnetic ink has been available for years to print onto fake checks (the account digits are MICR -- not just a pretty font)

Side note: One of the techniques that check kiters used to extend the float time was to erase the info encoded into the magnetic ink, which meant the routing & account numbers had to be typed in by hand at the processing center. The introduction of character recognition software means that technique is no longer usable.

they always did have a magnetic area under the 'united states of america' for bill readers.