As I have explained in the official support ticket you have opened regarding this matter there is a problem in the Batch EditMode where values which contain a group separator are used(please review this
link). We are currently researching the matter and will provide a fix for it as soon as possible. For now as a workaround I suggest using a GridBoundColumn without a DataFormatString so that the value can be interpreted as string instead of decimal.
Regarding the problem in the online demo. The UnitPrice field is defined as decimal(5, 2) in the database which means that the number may consist of five digits two of which should be placed after the decimal point. That said entering a value which consists of six digits(so that a group separator can appear) will cause a different kind error and is not related to the above mentioned issue.
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