Don't offer to save 20%, that's a minor benefit. The sales team will still be working that time. Offer to increase sales 25%. That's a serious improvement. ((100-80)/100 = 25%)
You can only reduce costs by so much. And each time you reduce them, you make it harder to reduce them further.
But if you can increase sales or increase profits, then there's no limit to how high you can go.
Focus on the positive things you can bring to the upside, not the things you can do to reduce the downside.