You’ve got your ceiling. You’ve got your industry averages. Now let’s factor in the other incentives you can offer. One of the best ways to motivate affiliates is to give them something to help them feel like part of the family. From exclusive deals & events, to branded merch, to just excellent partner care & service; think about what your specific company can offer reps that can a) endear them to your brand, and b) help you stay competitive without strictly relying on monetary compensation.
Finally, it is also possible to motivate the longtail of affiliates by offering them bespoke rates for hitting sales targets/increasing the visibility of your campaign across their sites. This could include writing reviews on products/services that you offer. Longtail affiliates are unlikely to hit a sales tier but if they are worked with closely, they are able to increase the sales they are driving with a minimal additional cost to the advertiser, with fantastic, targeted branding attached.