Reset converted_price when currency or price changes

games/models.py

@@ -164,6 +164,16 @@ class Purchase(models.Model):
             raise ValidationError(
                 f"{self.get_type_display()} must have a related purchase."
             )
+        if self.pk is not None:
+            # Retrieve the existing instance from the database
+            existing_purchase = Purchase.objects.get(pk=self.pk)
+            # If price has changed, reset converted fields
+            if (
+                existing_purchase.price != self.price
+                or existing_purchase.price_currency != self.price_currency
+            ):
+                self.converted_price = None
+                self.converted_currency = None
         super().save(*args, **kwargs)