Paid anchorages

Hello everyone
I was wondering at what point can someone charge you for anchoring in paid anchorage? I was anchoring in a undisclosed protected anchorage in Croatia, there must have been over 30 other sailboats. We went in found our spot, set our anchor and went on to make our lunch. Ten minutes later, out of nowhere, three huge dudes (sorry for my wacky description) come speeding on dinghy catch onto the side of our catamaran, no hello, no how are you today or any of that......they just ask if we want to stay in this anchorage. I said yes, but when they said the price my jaw dropped. 800 Croatian kuna= around 105 euros. That's the price for a fully equipped marina in that area. I said that we can't afford to pay that and even if we could, we would rather spend it on marina. That's when all hell broke loose. One of those dudes stepped on board - unauthorized, (mind you im 162cm and 60kg, he was at least double my weight), scared the sh*t out of me, and demanded that we must pay, since we already anchored. I said that we're leaving and locked myself inside until he went back into the dinghy. Someone from neighbouring sailboat heard our arguing and went to check if I'm ok. He also testified that I was in the anchorage just under 15 minutes. We picked our anchor and went as far away from there as possible. Sorry for the ridiculously long post, but Im still mad about all of it. Anyway the short answer is : once we set our anchor, can they charge us right away? Or should we have an option to leave immediately?

Sounds to me like a scam. Bloody scary for you though 

I was so shocked that I forgot to ask for id. It's possible that they were just some scammers. Especially considering how quickly they disappeared once the other sailor got involved.

Indeed, it is very similar to scammers counting on quick fear, so that the victim does not have time to realize or understand anything.