Costco appears to have a special version of the Surface Go which is much better value than the two versions Microsoft offers.
Officially Microsoft sells a 4GB RAM and 64GB eMMC storage version for $399 and 8GB RAM and 128GB SSD version for $549. The earlier version with 4GB RAM and eMMC storage is less than ideal, meaning unless it is to be used by children, most will go for the more expensive device.
Now it appears Costco is selling a variant of the device with 4 GB of RAM and 128 GB SDD, which is a much better combination. The device costs $549, but comes with a free black Type Cover worth $99, meaning users end up paying only $50 to upgrade to more and faster storage.
Of course, you need to be a Costco member to take advantage of the deal, but those lucky enough can see it here.