This rule monitors individual high-value refund transactions that represent significant financial risk if fraudulent.

Alerts when:
1. Single refund transaction exceeds high-value threshold
2. Refund amount is substantial regardless of merchant size
3. Transaction represents elevated fraud/loss exposure

Large individual refunds warrant scrutiny because:
- Significant financial impact if fraudulent
- Uncommon even for legitimate high-volume merchants
- May indicate merchant account compromise
- Could be authorized by unauthorized employee
- Potential money laundering red flag
- High risk of merchant dispute/chargeback

Alert-based approach allows:
- Real-time fraud analyst review
- Merchant contact to verify refund authorization
- Documentation review (return receipt, cancellation proof)
- Validation against original purchase transaction
- Pattern analysis for systematic fraud

Alerts without automatic HOLD to enable legitimate business operations while maintaining oversight on high-risk refund activity.