This is not about “paying for dates”. This is about after a shidduch goes to completion (even if not engaged) appreciating and compensating the shadchan appropriately for what they have provided. It makes all the difference in the world and shadchanim (being that they are human like the rest of us) respond very positively to it.
By and large shadchanim are not “for sale” as they don’t want to be beholden to any one individual.