Weregild was not a penalty, and had nothing to do with guilt. It was debt towards family to compensate for their economic loss with no consideration of "guilt" whatsoever.
The wikipedia page also says that
The payment of weregild was an important legal mechanism in early Germanic society; the other common form of legal reparation at this time was blood revenge.
Emphasis added. How is legal blood revenge consistent with the interpretation of murder as nothing but an economic debt owed to the family?
ETA: Besides which, even if murder were only bad because of the financial loss to the extended family, murder would still be bad. Giving a reason why murder is bad isn't to say that murder is not bad.
Your paradigm blinds you to reality.
There was no "murder", no "guilt", and no "penalty", and no "legal reparation" (in narrow modern sense) anywhere here. These concepts make no sense in such cultures. Intentional killing is treated identically to a common accident.
For another example - killing own babies was extremely widespread, not even condemned in any way in most cultures including pre-Christian Rome. It was just as casual as abortion is today.
Or killing family members who disgraced your family in any way (your ...
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