I understand your concerns. I have similar ones. However, I’ve been to at least one Retreat Center that charged a base rate, but barely seemed to be surviving. So perhaps whether the Retreat Center charges is something to consider, but not necessarily mean it’s a bad option depending on the totality of the circumstances.
For example, I was heavily immersed in goenka Retreats for years. They were donation-based and run really well. However, there were limitations for me at least anyway. And I wanted to explore different approaches to meditation. The only other Retreats I could find did cost a set amount unless one qualified for a scholarship. However, it was very worth it for me to explore those other options.
Anyway, just some factors to consider.