I’m really interresting about this topic. Because I hate seing fan to pay for a non-legal thing that doesn’t really help the ones who made all the TV show!

In Subarashii-no-Fansub, the cost for the subs is very low: ~$10 per month for 1To of data for a personnal dedicated server (yes, not a really dedicated for only the fansub).
But in an other hand:

• we have no encode server; we don’t really encode but use existing encode.
  If one day we must to encode, a personnal computer will be sufficient.
• we don’t have storage server. Even if our total size of project is less than 1To, I seed it for 3/4 months only.
  If one day you want my release, you must to download the encode + the pack of subtitles/font and mux them.
• we have a website on GitHub.
  I sometimes use hostinger to host a few file (free account) + sync.com services (free account too)

Other extras

Some groups only ask donation for paying BD. It’s not my goal to explain this kind of expense.
I prefer to annalyze the cost of the architecture.

For DameDesuYo:

They use IRC for chatting (a public channel + a private channel);

We can see that a simple site that receiving more than 20 000 visitors pay a low price (using cloudflare, a free account I think + the cheapest namecheap’s Shared Hosting offer), and a normal-price seedbox!
For encode server, it’s their choice that I don’t really agree. I hope one day this kind of server will be sharing between all the subbing group to be less expensive.
And for storage/ftp server, to receive big file (like .ts or .iso for BDMV) and store all their release, it’s expensive!

For others fansubs

They buy in general a dedicated server (for FTP/XDCC/Storage).
Some have that at ~18€ per months for 2TB. With the server, they can have private FTP for subbing processs, XDCCs, website + direct link. And the chat is on a existing IRC server.
Others have money (by themself or by using donation) and buy approximatively 100€/months (RDP server to encode + dedicated server at 80€ + a dedicated server for hosting (20€).
Hosting can be done in a blog-enterprise if content is not really licensed…