We just had one at Typhoon this past Thursday. After taxes it ended up being just over $400 for their most basic option. The largest one would've been $100 more plus tax. Some things to note:
As someone else said, if you're party size is larger than 6 then get the bigger one. While they do allow up to 10 in the standard unit, our group all noticed that it really would've been cramped had our group been bigger. We had five so it was perfect but no way I could've imagined 8 in there let alone 10.
The area where ours was located was in a roped-off section. The rope was let down once we were let in but they kept the sign up that said "reservations only." Also, I think all the chairs in the area that aren't cabanas are the umbrella chairs that require reservations too so that likely help keep those out that shouldn't be there. They also gave everyone wristbands to signify that we "belonged" there but there was never a time where we had to show it to anyone. We thankfully didn't have any problems with people in our cabana.
The attendant we had was great. They give you a number to text if you need anything and she responded very quickly. Even when we didn't text, she would check in on us at least once per hour to see if we needed new towels, more water bottles, or additional food/drinks.
They have family packs on the cabana menus that aren't available when ordering in person. By Disney standards, the pricing was much better than ordering separate meals for each person.
I don't know if it was a one-off when we were there that day but although she was very attentive, it seemed like it took a long time to get anything we ordered. By long time I mean at least 30 minutes, even for bar drinks. I know that's not necessarily the attendant's fault because everything was hot when we did get it but when the park's only open 7 hours, 30+ minutes isn't insignificant. Had I known that beforehand, I would've ordered and then left to ride more things and then came back later. Rookie mistake I guess. It didn't help that we lost about 2 hours of park time due to two separate storms but of course it never stormed while waiting for food.
Make sure you bring cash to tip your attendant. When we got the bill at the end of the day, there were two tabs. One for the bar and one for the food. The bar tab had a tip line but the food tab did not. So I said I would just put the proper tip for the combined total on the bar tab and she clarified that the tip line on the bar tab is for the bartender only, not her. So I asked how can I tip her (was using magic band to pay) and she said the only way she can be tipped is with cash. Thankfully I had cash so all was well but had I not, I would've felt really crappy. They should change that.
Was it worth it? That's obviously subjective but I will say I'm glad we had it. Especially due to the storms because they clarified that they are safe to stay in during the storms even if there's lightning (which there was that day). But I still felt $400 was pretty steep, especially considering how much better the cabanas are at Volcano Bay for the same price. But, if and when we go back I would do it again just for the convenience of everything and guaranteed shade.