Until it doesn't. We're not talking about the same thing here because one is a one-time payment (license) vs on-going (loot boxes / SaaS). I'm highly critical of loot box (p2p) games, but you're on-going payments do pay for content in the future. Companies who charge once have very little incentive to maintain the software (assuming it requires it to).
Because Elden Ring took 4 years to develop, 5 years if you include the DLC release time. You would need to amortize its very front-loaded revenue over those 5 years, because a live-service game like Diablo Immortal would be generating somewhat consistent revenue throughout that entire time.
Let's say ER reaches 20M + 8Mx2 for it's two upcoming DLCs @ $40 each. That's $1.8B lifetime. Pretty amazing! DI would need to make $360M per year to be an equivalent business. So 800k in the first 24 hours is not too far off track to being equivalent.