I'm not sure why you are considering giving money to Amazon, please don't, they can go fuck themselves. They lock you into using their services forever by having large egress fees for moving your data out. The popular open source NixOS project was hit with this recently and it highlighted this predatory issue: https://discourse.nixos.org/t/the-nixos-foundations-call-to-action-s3-costs-require-community-support/28672
Do you really have more than a few TB of data? I would be surprised if you do. Just use a cheap VPS for storage: https://contabo.com/en/storage-vps/ has 2.4TB for 18$/month. Contabo has famously shitty support but they still have it and my experience with it has shown me that the cheap makes up for it.
I actually don't understand how a wiki with 22,000 pages of text and 4,000 files can be "very costly" to host. Please don't go the wikipedia route with the expenses.