I think this is a very good question, – to be asked of a posaik, not to be resolved here in the CR.
The reality is that shidduch dates ARE expensive, and (since boys in the shidduch parsha are generally in yeshiva and/or college, and NOT working) they are usually paid for by the boy’s FATHER.
The question IS then, can he (the boy’s father) pay for his son’s shidduch dates from HIS maaser money?
If anyone has gotten an answer from a Rov on this question, I would be very interested to hear it.