Your numbers are perfectly accurate as of the last census. Admittedly, only SE knows the real number today. While mine was more of a guesstimate, the ratio I used 4:1 was apparently pretty darn close. I'll quote your numbers in the future.
You have good points that I think I already agreed to. If not, I agree. The currency for relics can be done for free and soloed in about 120 hours assuming you have a few of the correct jobs / subjobs. There are of course other tasks and those aren't going to cost gil either. There's time to get the attestation, fragment, 5 x kills of test NM plus ~1,400 kill-shots. What does that take? 30 hours? Maybe more. Some of these are real hateful time sinks.
If we compare it to empys, they 'can' also be free, and as you said, they will be easier. I'm not going to say you can do one from start to level 90 in a weekend, but people don't take 150 game hours to do them. So empy is certainly well ahead of the relic at that point.
Now, not to debate this, but the currency farming issue is a two-edged sword. If you can do the empy from 75 to 90 in 100 game hours, you can spend the 'saved' 50 hours farming 6,250 currency for ~50,000,000 gil. That opportunity cost is hidden unless we see that while both weapons 'can' be free, the relic is never really free.
People will argue as well that you can buy the pops for empys and do them much faster than 100 hours and in so doing save even more time to make even more gil. I'm not going to argue that. I just want to point out that, they aren't 'equally' free.
Yes agree
We may not know this for a while. I don't think the relics are cheaper or easier depending on how you accept my point about opportunity cost. But the story isn't clear on rift drops or ADL.
We do need the content for both to stay relevant.