Microsoft's UFS storage surcharges, German prices in € incl. VAT:
+_64GB +€120 +192GB +€240
For comparison, Samsung M.2 SSDs in the retail market: _64GB outdated 128GB outdated 256GB €_23 512GB €_34 __1TB €_40 __2TB €_95 __4TB €282
Some other manufacturers offer cheaper SSDs.
Microsoft tries to pull the total rip-off. UFS is worse technology than SSD. The prices per GB are exaggerated by up to the factor 50. Apple can do it so Microsoft thinks it can also do it. There is a reason why Microsoft does not enable replaceable storage while every other component becomes replaceable. It wants to treat the potential customers as idiots.
Microsoft advertises the new Surface Go 4 as being exclusively for businesses. However, the new 2-in-1 is available to order freely in multiple countries, including the US. The Surface Go 4 starts at US$579.99 with Intel Processor N200, 8 GB of RAM and 64 GB of storage.