Hi Medusa,
It's not "necessary" and I am aware that people are struggling. I am as well. But I'm just putting everything out there to see what people want to do. If we agree on getting the cabana and you can't contribute I'm sure that will be fine.
Being that we are struggling this is will likely be our only vacation all year so, for me an additional $50 where we can relax privately, with a TV and in the shade by the pool with an assistant to bring us drinks and towels, etc... is worth it. Depending on how many people are on board, and my finances, I will take care of what is left over. And all will be welcome.