During the twins' expedition in New York City, their path included the Chinatown area of Manhattan. Chinatown is approximately 4 miles (as the crow flies) from 600 East 62nd Street, the address of their apartment building as stated by Mr. French, in S1 E4, The Matter of School.
The $20 bill that Buffy and Jody find would have about $183 buying power in 2023.