The same people that pay for the FIA-approved racing fuel and refueling zones....

which in the end is the participants.(drivers/teams).

Both directly (fuel cost) and indirectly (entry fees to rallies/championship).

Obviously with high investment cost and low running cost+reuse it makes little sense for every rally (or competition) to buy their own. So FIA/national organization has a competion for charging supplier who gets fixed sum+payment per driver on each rally. (Again either entry fee or "pay per kWh").


"But it will be so expensive".
Quick calculation is: 3 MWh Tesla megapack is about 1 mil.
Assuming 50 kWh batteries in each car that's 60 cars. So on normal rallies with 100 cars you need 2 + say 2 recharging themselves ( that ignores any chance of connecting to the grid at the rally car recharging location). So 4 mil.

Now the big question is how you utilize those? For one championship that has a rally once per month? That wouldn't make sense. Let's say you share it with 3 championships that have 6 rallies each.
4 mil/(18*100)=2,2k euros per car and rally.

That's assuming the trucks last one year. If we assume some replacement needs and say they last 3 years on average you get 700 euro per car and rally. That doesn't sound too bad.
Obviously these are very approximate figures but I'd assume they are not orders of magnitude wrong.


Anyway it still makes more sense to try to use existing infrastructure (charging stations) as much as possible. Cause as I mentioned and you ignored. The big difference between petrol and electric cars is that electricity (converted) is same for everyone and those converters (AC/DC, voltage etc) are not oil-rafinery sized.