Only problem is, for non-paying players who didn't store any magas or have low level/stamina cap, or don't have time to play each few hours to utilize as much passive regeneration as possible, even reaching that 100k mark will be hard.
400k points is 13.(3)k points per day. 500k points is 16.(6)k points per day.
Assuming you will use only 165 free magas you get from rewards you have 5.5 magas per day.
Assuming you need high enough stamina cap we can use 480 stamina per day you will regenerate sleeping/playing which is 14.4k stamina total over 30 days.
With that 860 points per 100 stamina you mentioned (4 games with 65 average and 600 per bonus map spawned with it) we get 8.6 points/stamina ratio.
With that 14.4k stamina you would then get close to 124k points over whole event from passive regeneration, you need then:
276k points more which is 9.2k points per day to hit 400k, which is 1070 stamina (9.2k/8.6) per day, which with 5.5 magas per day means you need to have a 195 stamina cap.
376k points more which is 12.5(3)k points per day to hit 500k, which is 1458 stamina (12,5(3)k/8.6), which with 5.5 magas per day means you need to have a 265 stamina cap.
Yeah. 100k points is 3334 points a day. Which with 8.6 ratio means 388 stamina per day burned. But just to add - you can have 480 stamina per day from passive regeneration if you don't sleep, or have high enough stamina cap (at least 160 to sleep 8h ).