Opinions Requested: How many days of © savings is Rend Armor worth?

I was going to ask if it's worth 500B, but that's clearly not a fixed value, since some of you earn that in a single run.

I'm currently earning about 200M/day so I'm wondering if it's worth saving for 2.5(ish) days to unlock or if I should wait until 500B isn't such a big chunk.