In this case, where the supplier has been involved in almost every aspect of the project, the design portion could be on the lower end of this range since they are also managing manufacturing, logistics, and coordination. For a typical custom PCB project with the involvement described, design work could represent around 25% to 35% of the overall effort.
Well I haven’t, maybe explain how I’m wrong instead of posting a standalone quote which doesn’t even contradict my assertion. I said “I guess” because I have no clue what takes more work, that was my initial impression.