Odds are extremely low 1 in a 10 million excluding winning chance odds It should be over 400BTC to be EV+
That number seemed way out there, so I checked. Let's take a few seconds to go over the calculation together, instead of just throwing around made-up thresholds:
The house edge on dice is 0.8%.
If we assume you wager at a x2 payout (most common, probably, easy for an estimation), that would mean you have to wager 0.00000100 per bet to qualify for a dice jackpot.
If it takes you on average 10 million tries to win a jackpot (the expected value), then you would wager 0.00000100*10000000 = 10 BTC in that process.
Of course betting at this size will only award you 1% of the jackpot share. That 1% would have to match your expected losses while wagering 10 BTC to bring you to +EV.
So how much are you expected to lose when wagering 10 BTC? Well, easy enough 10*0.008 = 0.08 BTC.
So if you are playing in an area that gives you 1% jackpot hits, you would need to recoup 0.08 BTC from the Jackpot for it to become +EV.
Since the 1% is easy to calculate, we can quickly see from which jackpot balance up this is the case, 0.08*100 = 8 BTC.
The threshold for 1% jackpot hits to become +EV is not 400, it is way less than that, 8 (or roughly 2 times the current balance, raising as we speak, since the jackpot is progressive).
Now you might claim that the difference of roughly 5000% does not matter, because the situation is the same, the balance for the jackpot to become +EV is higher than the current jackpot balance.
But I'd say it makes a big difference, not just for people playing right now that can shave a big portion off their house edge with the jackpots (and even more if they participate and place in the wagering contests), but also for the future.
I can see the jackpot growing to 8 BTC or higher, that seems like a reasonable number, I however cannot see the jackpot growing to 400 BTC anytime soon, if ever (which is probably why you threw around such a stupidly high number).