Gilboa is one of my favorite places to dive. When I was in Hawaii diving with Justleesa, I found myself looking forward to diving my dear, ol' quarry! I won't be able to dive again until next spring/summer and I find myself looking forward to paying that $19 again!
The "parking" fee isn't technically for parking, though they don't explain it very well. The last I had this discussion with them, the "parking" fee is actually a "campsite usage" fee. Meaning that if you're going to be up top where all the cars park and have your gear up there, you'll be paying for the usage of that space- the "free area" is down on the tables by the ladders to the dock. So the BS "per person" fee isn't really for parking, it's for camping area usage (which is different from paying for a camping site). They have limited space up there. Their party; their rules.
I haven't been there since spring but that was the case then. But they don't explain it very well.
Regardless, I've paid $20 at Blue Springs just to get in. And both Portage and White Star are further for me (I drive north). Plus, Gilboa has IMO very good facilities.