At Shutterstock anything above 500,000 copies needs an Extended License, but if they can't get it there you have them at your advantage.   If you are unlikely to do buseiness with them again you can charge a priemium on what Shutterstock charge, if they might want more give them a discount, $100 would be in the middle.  It dosen't matter what license you give them as you are unlikely to be able to enforce it, once you let it go they could do anything with it, so I would go the premium route.