Data Deployment Error: FIELD_INTEGRITY_EXCEPTION:This price definition already exists in this price book

When doing a data deployment, Salesforce may return the following error:

“FIELD_INTEGRITY_EXCEPTION:This price definition already exists in this price book”
 
Price Book entries fail to upsert when you include UnitPrice in the composite external ID. 

To fix this issue, remove UnitPrice from your composite external ID.

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