Wolf,
I don’t think I am in disagreement with Chein. He is correct that what must be paid is dictated by halacha, not personal feeling. If the shadchan did not perform the service with intent to charge, then halacha dictates that there is no obligation.
When you do a photography job pro bono, are you doing anything wrong by not charging? No! It’s the same with shadchanus.
Besides, Chein was referring to what must be paid, and you’re talking about what must be charged.