For the Russians break even point for oil is around $40 or so if I am not mistaken.
They have been pumping oil money into national wealth fund that is used to keep social and political peace.
Saudis pretty much don’t have anything but the oil.
They will drive shale oil producers out of business but there is no way for S.A and Russia to last several years, especially Saudis.
Saudis are surrounded with enemies and any arms embargo would put them in grave danger.
Majority of their equipment is bought from the U.S, that includes parts, munitions, training etc.
For example all combat helicopters are U.S made, as well as 4000 tanks and armored vehicles.
By the time they get re supplied and re trained on new weapon systems from China, Russia etc. they will be long dead.