As the title says. The odds are heavily stacked against you, so unless you feel like degen gambling a bit, the better EV play would be to unbox the "very rare", stop, and buy the ultra rare on the market in a few days.
On average, a user can expect to unbox the very rare between 15-30 opens (average in low 20's). The cost of the tiny ultra rare after a few days is ~ around 10 caches. The base set is probably useless close to useless to you unless you want to gift a friend, recycle for a fraction of the value, or have the patience/experience to gift trade, so odds are you don't care about getting more dupes.
Even assuming you opened 30 already b4 the very rare, the odds of you getting the Ultra rare in 10 more treasures has a culmulative probability of 31%. You have culm ~27% chance to "profit" (ie: spend less than if you bought it on the market), and a 69% of spending more. And again, this is assuming you're already super unlucky and took 30 treasures to get the very rare – odds are these odds are gonna be even worse.
So yeah, don't get jebaited. Valve adds level rewards to incentivize players to get at least 14 – after that the escalating odds start jebaiting. Don't fall for it.
Source: https://www.reddit.com/r/DotA2/comments/zszt8y/psa_if_youre_going_for_an_ultra_rare_do_not_get/
