International System of Units
I think the game should be in accordance with the "General Conference on Weights and Measures". Let's say I have 1.4K of Ice in my inventory, in-game: Mass = 1,400.00 kg; Volume = 518.00 L.
"The 22nd General Conference on Weights and Measures declared in 2003 that "the symbol for the decimal marker shall be either the point on the line or the comma on the line". It further reaffirmed that "numbers may be divided in groups of three in order to facilitate reading; neither dots nor commas are ever inserted in the spaces between groups" (e.g. 1000000000). This usage has therefore been recommended by technical organizations, such as the United States' National Institute of Standards and Technology.
ISO-8601 also stipulates normative notation based on SI conventions, adding that the comma is preferred over the full stop."
So, the "correct" form should be: 1.4K of Ice; Mass = 1 400,00 kg or 1.400,00 kg; Volume = 518,00 L.
https://en.wikipedia.org/wiki/International_System_of_Units - "Lexicographic convenctions" section; "General rules" sub-section.