I was going to reply "about as much as they cost normally" but I see you're not used to having them home all the time XD
Although if you add up all the fees you would pay for their extracurricular activities and kids' club and whatever else you might find it's working out similar and the hardest thing is there being only you instead of all the other adults they could go to for help XD
In CZ kids have to wear facemasks in school, in class, all lessons
Pso I'm seriously thinking of schooling at home