3 SNES games should come in slighly underneath a pound (around 13 to 14 ounces) so if you can keep the combined weight with packaging under a pound it would be around $5-$6 for first-class international or $12 for priority (EDIT: Priority flat-rate, that is).
Curious if you still have Dynasty Warriors Gundam 3? If you do and are willing to trade please let me know and CML. Also, I do have some extra MSP left.