In July last year, it was revealed that Costco was selling a slightly better version of the Surface Go with 4GB of RAM and 128 GB of SSD storage to its members. This device sat between the generally available 4GB/64GB eMMC storage and 8GB/256GB RAM SSD Storage version everyone else could get.
In November Microsoft made that version available to everyone else, but today Neowin noticed that the better configuration was no longer available.
Now if you want 128 GB of RAM you have to spend $150 more than the base model for the 8 GB RAM version.
While I am sure most users would prefer more RAM over increased (expandable) storage, the 128 GB storage was of the SSD kind rather than eMMC, bringing its own performance benefits.
The other configurations can still be seen at Microsoft here but you can still find the “Costco” version from, of course, Costco as well.