How much are Birthday parties?

Depending on how many people.

Depending on how many people you are inviting. You can also just rent a cabana and get cake, food and snacks with them and see if that price is better for you. Coordinate with them for a better pricing.

What I did was book a cabana already and called the birthday coordinator and she help me set up with cake and pizza and that was it. There's not much else you really need to do since the water slides will be entertainment for your guests

They vary its per person.