We just had the same scenario: one error in a service flooded out our account limit, but each successive logging of the error provided no additional information. Fortunately, it happened at the end of our billing cycle, but we could have lost use of Raygun for a month if this had happened earlier in the month.
Realistically, if we have a thousand or more reports of an error, we aren't getting more value out of additional copies of the report.
It might be nice to know how many times the error happened for prioritization, so a bonus to this change would be that the error count could reflect the dropped errors even though the reports were not stored. However, that isn't the most important part.