First off, to Rade Konn: Welcome to the Myriad Manifest!
Second, after the topic came up briefly in another thread, I looked at the historical rank requirements and payouts, and will now make a more simple way of showing the requirements for Elite plus.
At release, getting Elite in exploration required ~156 million Cr scan profits, and at the very beginning, an undiscovered(!) ELW or WWTC would net you a bit over 45k Cr. Which, after a simple calculation, is a whopping 3,467 WWTC/ELWs scanned. It's little wonder that in 3301 March (ED 1.2.03), they doubled payouts while keeping the rank requirement the same. Going with a 90k Cr median, that would be 1,734 WWTC/ELWs.
We'll be using that as the basis for Elite Plus calculation then: basically, the credit value will be tied to how many credits one can get from finding 1,734 WWTC/ELWs in a given version. (If ELWs will actually pay more in a future version, then we'll go with WWTCs from then on.)
Do note that since ED 2.3, payout credits contribute half their value towards rank progression. (This was put in alongside a payout increase that went as high as 9x.) So the original 156 million Cr rank requirement effectively became twice that, the 300-320 million Cr that we're all familiar with. Passenger mission payouts contribute even less. Think of it as needing 156 million XP, and each 2 Cr data sale providing 1 XP.
With that in mind, the current payout value for an undiscovered WWTC/ELW of median mass is 3.2 million Cr. 1,734 of those will come to 5,548,800,000 Cr. However, we need to halve that, the final result is: 2,774,400,000 Cr required to get Elite the original way.
To make it easier to remember, let's go with 2.75 billion Cr.
This is 0.75 billion higher than what I calculated before, but I had some errors in that. My bad on this. I don't think anyone would no longer qualify based on this, but even if such happened, I'm not going to remove it from anyone.
A body count would also be pretty good, but I'm not sure if there's any third-party program that can give you a count of how many undiscovered bodies you've sold. If there is, do let me know! Such a count would serve as proof as well.