AU50
This is a like new machine according to Comgrow, price reference below, you can decide if the price difference justifies.
"These 3D printers are from customers' first purchase and were returned to Comgrow amazon store and online store without the customer taking delivery. These machines have been professionally inspected and we guarantee that these printers are 99.99% in the same condition as a new printer
"
New machine price steady at $A578 https://au.camelcamelcamel.com/product/B07DYL9B2S
Extra review https://www.youtube.com/watch?v=Ikc8qnlHpY8
The Creality store themselves are selling brand new Ender-3 S1's for ~$57 more. I'd personally spend the extra $57 for a new one, especially since the product itself is $500+. But that comes down to personal preference, I guess.