Dunno:
If shadchanim where compensated for bringing about date number 2 and date number 4 then
1. we would have hundreds more quality shadchanim
2. slightly older girls would get tons of attention
3. it would be better for all the girls as many many more people would be looking out for them.
I’m not saying its a halachic obligation (it’s not so long as that has not yet become standard minhag). I’m simply saying that it will work and it will make shidduchim easier all around. Not by paying ahead of time for their attention, but instead by treating them like successes if your child goes to a date numbe 2 and date number 4.
Communities that have tried are very very pleased witht he results and other communities and org are looking to duplicate it.
Demo: your post is great, except that pre-paying isn’t nearly as effective as showing appreication and compensating for whatever quality attention you received.