Always been 45K or 35K no inbetween
I can do it with 3 hrs play per day using rank 2 event vehicles in GRB.
3 hrs is an evening - so my evenings are shot for the time of the event, but it’s an “EVENT” - not a giveaway.
Except when it is 30,000 of course!! :)
The cost has always depended on the rank of the vehicle - higher ranks are 45k, lower ranks have always had lower costs.
Naval gives you a 1.9 multiplier for AB and 2.2 or 2.3 for RB - it is by far and away the quickest of these events!!
I think the key is just to play the tank that you’re actually good at, no need to torture yourself with playing a tank that youre not familiar ini, say i have top tier germany but ive been grinding the event with the british 4,7 and its been a blast