HOWEVER, they (shadchanim) don’t feel comfortable doing so at the begining, and their lack of comfort level is to a large extent due to how they will be perceived if they were to do it.”
Sorry, but if it is an “accepted and well-known practice” to be paid a “going rate” then most people expect the shadchan to charge for the service, by your own acknowledgement. It’s just a matter of defining the parameters. And just as with any other business, the customer should be told the price before agreeing to the service.