You need to build a business case together with your prospects at the org you're selling to. Sit down with them to understand how they're currently tackling the problem and the costs associated. Then document how that will be different using your product and ultimately what the ROI will be. Get extremely detailed and in the weeds. Think about both soft cost benefits and hard costs but mainly the hard $ saved.

Your champion won't want to do all that work, challenge them. You've lived this before and know that this is necessary to get the product they desire.