I would do all these calculations on the server side. Probably returned with extended domains/users api requests, or maybe better via /api/v4/wallet/{wallet-id} (which does not exist yet).

I'm not sure also if these tables need to be so prominent here. Maybe it should be displayed on request. I'm thinking that we we'll need a place to display wallet history and payment receipts somewhere. Which of these is more important to display in the wallet and which should be loaded on request or completely moved from wallet page?

Partially implemented in https://git.kolab.org/D1372 and we decided to not implement the costs overview table. So, I think this differential could be abandoned.