Nope. nada. zilch. If you have an outstanding program that offers more than anyone around them I've heard of it being done to eliminate the curious. They want the serious athletes. It can also act as a fundraiser for the program. Personally, I would never have my DD attend one.
There is a team in my area who charges the players a fee and returns it to them if they stay the whole season. The coach does one team and they are usually average at best.
Stupid, and that's being nice. If the girl is good enough to make it on most teams she'd try out for, no way would that parent be interested in paying. They'd just go to another team. Seems to me it'd be the desperate parents actually willing to pay for the "chance" their DD could make the team.
A couple of the big orgs do it here. They do it for fundraising and because they can. There are a lot of parents (I say that because we're 12U and most of the girls still don't care about the Big Orgs) who really, really want their kid on that big name team. They're willing to pay to get her in front of the coaches, even though said team probably is either full by tryouts or has maybe 1 or 2 spots left for the diamond in the rough that might possibly show up at a cattle call. I imagine the odds of being chosen at one of them are not very good.
The only paid tryout we ever did was for the USA Elite Select Futures team in 10U. We did that for the evaluation and getting to meet the Pride players. It was really fun, she had a great time.
We paid for DD to tryout with one of the local marquee organizations once. Went to the tryouts, DD did well, they had six coaches there and we NEVER heard back from anyone...
Sometimes there are fees for the tryout facility. If you have three open tryouts that can add up. I don't' see anything wrong with charging a few dollars to cover the facility fee.
It's a drop in the bucket when you compare it to all of the money you are paying for travel softball.