Well! In my circles it has always been a gift, that is what has been customary. And believe me we give beautiful gifts and no one complained. For our first two shadchanim we bought beautiful silver vases. For the last shadchan I found a beautiful silver tea service that we split with the mechutanim. Again, the shadchan (only one) was very surprised and happy.
All three shadchanim would have felt awkward to receive a cash gift from us. When spouting your facts please be aware that not every situation is exactly as YOU KNOW IT TO BE. Not everything is according to YOUR perspective or your point of view. Other people also know what they are doing and how to handle their own situations. And others are NOT wrong for doing it their way.