It wasn’t that long ago that the Royal Equestrian Mint made one-bit coins available to us non-pony folk, and given the utter absence of an official, or even an unofficial, exchange rate, I suspect most of them are being sold as objets d’art.
Still, one bit is not an enormous sum, which may or may not have motivated this interested party into reproducing Equestrian paper currency. Denominations are as follows:
One: Princess Celestia
Two: Twilight Sparkle
Five: Rainbow Dash
One Hundred: Pinkie Pie
One Thousand: Princess Luna
I have no idea what, if any, rate of inflation may prevail.