In Old Zhou's case, the client thought the commission wasn't worth it because they couldn't see what that fee bought them. If clients can get the same thing directly from the factory, the commission obviously has no value.
To make clients feel it's worth it, the key isn't to lower the price, but to make what you do 'visible' and 'hard to replicate':
First, make your work traceable—every price comparison, every delivery follow-up, every quality confirmation. If this only exists in your head, clients will never know what you did. Having records of these processes lets clients feel your effort.
Second, concentrate complexity on your end—if clients go to factories directly, they manage five of them, handle five delivery schedules, process five different document formats. But working with you means dealing with just one window. This reduction in complexity is your value.
Third, solve problems before they reach clients—quality issues, delivery delays, document errors. If you can handle these before they become your client's headaches, eventually clients will understand why having you is better than not having you.
Lowering price is the easiest choice, but it's also the quickest way to reach Old Zhou's fate.