Is the 20% Fee for Predictive Bid Shading Worth It in Your Programmatic Ads?

Hello, I'm currently using a Demand-Side Platform (DSP) that has introduced a service called 'predictive clearing pricing' or bid shading. This service is designed to optimize the amount you pay for ad impressions by predicting the lowest possible bid that will win the auction. However, they're charging a 20% fee based on the savings they generate for us. I'm wondering if this fee is common in the industry. More importantly, is it actually worth it, especially when we're focusing on last click conversions? Any insights or experiences would be greatly appreciated.