Let me guess. Your company doesn't have any metrics for your value proposition and you're wondering if it's possible to be successful. Absolutely.
1. Go talk to Your Clients
If they don't have exact metrics, perhaps you can suggest a range. You might say, "Gut level – do you think it helped cut costs somewhere between 8 – 10%?" They'll either say, "That's about right," or tell you if it's too high or too low. Either way, you now have some metrics you can use.