https://www.theverge.com/circuitbreaker/2018/11/6/18069086/microsoft-surface-go-costco-exclusive

Microsoft’s tiny laptop-tablet hybrid Surface Go originally came in two variants: a 4GB RAM, 64GB SSD budget model for $399 and an 8GB RAM, 128GB SSD model for $549. Then in July, Costco began selling a $549 bundle that included a Surface Go with 4GB of RAM, 128GB SSD, and the Surface Type Cover (which separately, would cost $99). Now the exclusive period on the Costco model is over, and the 4GB / 128GB variant has made its way to the Microsoft Store for $499. Unfortunately, it’s currently out of stock but a Microsoft spokesperson confirmed that the company is working to restock the model.