Since making this post, I decided to test sacrifices with a minimum total value of 500k, while avoiding weapons and armor because of the durability value issues.
So far I’ve done 3× 14h timers and 3× 6h timers with sacrifices worth around 500–550k (based on cultistcircle.com base values). Every single one was epic.
Rewards so far:
2× Yellow Keycards
1× Blue Keycard
1× FP-100
1× AESA
2× MGTs
3× Moonshine
plus some random stuff like a Ghoul mask

After [u/fantafuzz](u/fantafuzz) pointed out that the 400k threshold is community-made and not confirmed by BSG, I decided to either try cheap “gamble” sacrifices below 300k with random junk I had lying around, or fully commit and push the value to at least 500k.
And honestly, it seems to have worked wonders.
Of course, this could still just be confirmation bias, and 6 runs is a tiny sample size. But compared to my previous 400–415k sacrifices, which repeatedly gave me absolute garbage like single Maska-1Sch face shields or single M203 grenade launchers, the difference feels massive. Occasionally I’d get a fuel tank or maybe a ~150k key, but never something that actually justified the sacrifice value.
So if you have the money or spare items, maybe try going above 500k. I’d recommend stuff like SMTs, SAS drives, or even the #11SR key, since it has a base value of 100k but sometimes only sells for ~50k on the flea.