The First Online Purchase Was a Sting CD (Or Possibly Weed) (fastcompany.com)
tedlistens writes: On August 11, 1994, 21-year-old Dan Kohn, founder of a pioneering, online commerce site, made his first web sale. His customer, a friend of his in Philadelphia, spent $12.48, plus shipping costs on Sting's CD "Ten Summoner's Tales," in a transaction protected by PGP encryption. "Even if the N.S.A. was listening in, they couldn't get his credit card number," Kohn told a New York Times reporter in an article about NetMarket the following day. According to a new short video about the history of online shopping, there were a few precedents, including a weed deal between grad students on the ARPANET and a 74-year-old British grandmother who in 1984 used a Videotex—essentially a TV connected to telephone lines—to order margarine, eggs, and cornflakes.
I personally purchased things in the mid-1980's online using Quantum Link, but CompuServe dates back to 1969 so people were obviously making online purchases throughout the 1970's. BBSes were active and often linked together in massive networks from the 1970's through the 1990's. Whether that counts is up for debate.
If you're speaking strictly about the Internet, the Usenet forsale groups have been around for a long time. My first use of the Internet was in 1992 to sell some old computer junk, but Usenet dates back to the 1980's.
It's amazing how ignorant people are of the online world before 1995.