Of course people soon became tired of lugging tons of batteries around with them - and having to stand in line to get them charged up at the end of every work-day. Also, measuring the amount of charge transferred between your battery and that of the supermarket when buying a pound of carrots was always a matter of some dispute. Hence there came to be standard batteries with numerical displays on them to show how much charge remained. Places called banques sprang up where you could leave your batteries and read out their charge remotely. Exchanges allowed you to discharge your batteries *here* and to use an exactly equal amount of energy to charge up those of someone on the other side of the planet who wished to provide you with some physical goods. The inconvenience of physically storing all of that electricity made it more efficient for the banques to supply it to people who needed it, in exchange for electricity in return in the future. Over time, nobody was ever sure that the amount of electricity held in the banque was as much as the banque claimed to have stored - or owed to it.
Pretty soon, a shorthand word for "total amount of electricity" was needed - and that quirky unused '$' symbol on everyone's keyboard came to stand for some arbitrary amount of the stuff.