What is one Galactic Credit worth?

In real-world terms, the Galactic Credit seems to be roughly analogous to a US dollar although certain items are going to be massively cheaper as a result of droid labour or massively more expensive depending on the relative purchasing power of your credit, your distance from the Empire/Republic and the rarity of the item you're purchasing.

It's also worth distinguishing between Republic Credits (which not everyone accepts), Imperial Credits (which seem broadly acceptable everywhere) and New Republic Credits (which are pretty useless).

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• According to Rebel in the Ranks, a single credit will buy you a raffle ticket.

  “Hi,” one of them said breathlessly. “We’re selling raffle tickets to raise funds for our Junior Academy camping trip in the Westhills. Would you like to buy one? It’s for a good cause and a ticket is only one credit.”

• Six credits will buy you a meal on Five Points Station

  One hundred credits. She had to make it last. But first: food. Jyn slipped out of the reeking public bathroom stall and headed deeper into the station. She clung to the outer perimeter of the main floor, where the shops were smaller but cheaper. A bodega built between two towers of residential cubes looked local enough not to extort her too badly. She bought a can of nutritive milk that was dusty on top and a tube of dehydrated vegetable protein straws. Not the tastiest but definitely the healthiest, most filling option; this would last her the whole day if she was careful. Food was important. Hunger would make her careless, an easy target. Food and sleep were vital to survival. Ninety-four credits left.

  _{^{Rebel Rising}}

• A room for the night will cost you 13 credits.

  Maybe they just want to rob me, she thought. But she couldn’t be sure. An inn had rooms for rent, and Jyn passed over more of her meager supply of credits.
  Sixty-seven left.

  _{^{Rebel Rising}}

• A can of bug spray will set you back four credits (in a seller's market)

  “Nazgorigan’s patented bug repellent. Guaranteed to make the little bugs buzz off. How many would you like?”
  “Sorry?” Lina asked.
  “How many would you like to buy? You won’t get far on Thune without one can or seven. Unless you like scratching yourself until you’re raw, yes?”
  “Okay, we’ll take one,” Milo said, pulling a credit chip from his pocket. “How much?”
  “Four credits each,” the alien replied.
  “Four credits? That’s a bit expensive!” Milo said.

  _{^{Adventures in Wild Space}}

• Two alcoholic drinks in the Alcazar will cost you ten credits.

  “Two drinks. I’ll have a…” He turns to the Twi’lek. “You first, friend. What are you having?”
  “An…ale?”
  The Twi’lek looks nervous.
  Sinjir makes a face. “He’ll have an ale. I need something stronger. You got ahh, let’s see. Jogan fruit brandy?”
  “Kind of a fancy place you think this is?” the bartender rumbles. “I got ale. More ale. Other ale. Different ale. Grog. And starfire ’skee.”
  “I’ll take that last decoction, then. A jorum of ’skee for me.”
  The bartender grumbles. Begins pouring a glass of something brown and muddy before sliding a bottle of foaming ale to the Twi’lek. “That’ll be ten credits.”

  _{^{Star Wars: Aftermath}}