@matejrokos I am almost sure its impossible to get any idea or estimate. Volunteers don't do time tracking. Looking at an MR doesn't answer the question if a professional did that in half an hour or a hobby coder in three days.
The foundation numbers may give you an idea about cost for infrastructure. But only partially as well, since we use for instance free hosted weblate or contributors use their own free gitlab CI minutes, so they don't count on the foundation servers.
Volunteers also don't have funding. If they are lucky they get a "thanks" or some smaller donations. But that is not tracked at all.