This map shows which decimal separators are used in which country:
Source: Brilliant Maps
If in countries a period is used as a decimal separator, then the comma is used for groupings of thousands:
It costs £ 12,345,678.90
If not (and if you are not in the middle east region), then it is the other way round:
Es kostet € 12.345.678,90
In both cases there is no space after the comma (also no space after the period). The next character immediately after the separator is always another digit.
But when you put numbers in a list, the list separator consists of two characters, a comma and a space (or a tab or another white character):
These are the earnings of the last 4 month:
9,580.17, 8,845.37, 12,052.04, 10,522.86.
Das sind die Einnahmen der letzten 4 Monate:
9.580,17, 8.845,37, 12.052,04, 10.522,86.
It is clear in both cases, and I would say the readability is equal.
But if you want to make it even more clear, you can use a semicolon as separator:
9,580.17; 8,845.37; 12,052.04; 10,522.86
9.580,17; 8.845,37; 12.052,04; 10.522,86