Battery Quality

The last U.S. lead smelter closed in 2013,
For a while there was a premium on battery core that seems to have dropped off, battery cores seem to have fallen back to $30.00 to $60.00 per core.
There was also a surge on battery prices, that seems to have fallen back also.

This year I bought two group 31 (Commercial Truck sized 12 v)
Both batteries run well and take a charge

But...
Neither battery will hold a charge for any duration, if parked with a full charge, both rigs will start within 3 days, 4-5 days sitting and if its warm they start reluctantly, if cold not at all, within 2  weeks of sitting with about a 40 milliamp draw (computer) the batteries are so low a "smart" charger will tell me there's an open cell. a dumb charger will have to be employed just to get the voltage to a point where the "smart" charger will recognize it.

After charging and running to the parts store (about 1/2 hr away) the battery and charging system check out as ok. (14.2 v input 12.9 without input) with three days time on them, its down to 11.7 v static charge after 7 days 10.9v and dropping.

I also replaced the group 35 in my wifes car, within 3 months it exhibited the same symptoms, although it being half the size of a group 31 started having only one days grace, and by the second day was incapable of cranking the car. Both the battery and the charging system checked out on computer diagnostics.
I replaced it with an Optima redhead, and 8 months later it performs flawlessly. The car can sit in storage for months and starts without issue.
The price difference between a Standard battery and an Optima is roughly $150.00
(Standard $85.00, Optima $235.00)

I'm assuming that a standard battery is reconditioned, and somehow standards have been relaxed, so that detail is no longer included in sales info?
Has anyone else noticed this phenomena?

Are you sure both are lead acid batteries for this comparison? I suspect the Optima battery you purchased at the substantially higher price is not a flooded lead acid battery but rather an AGM (absorbed glass mat) or possibly one of those spiral cell batteries. I believe that this likely explains the performance difference you've been experiencing. Among flooded lead acid batteries, there are two kinds I am aware of, deep cycle and SLI's (starting, lighting, ignition). Deep cycles are good for constant current draw like in a solar systems, and the SLI's are rated often by cold cranking amps, and are made to handle massive current dumps to turn a starter in an automobile, whereas it's my understanding that using deep cycle batteries for starting engines can rapidly decrease the batteries life expectancy.

The EPA did close down the last lead ore smelter but secondary/recycling smelters are still working. The Optima and a regular BCI 31 or 35 are different animals. The spiral wound Optima for me has proven to be a very good battery. A group 31 should hold a charge much longer than you 're experiencing though with the minimal draw you have indicated. Are you in an extreme climate? The 31 is a pretty big battery for a normal rig what is the vehicle?

Both 31's are in in a 93 Dodge Diesels, The 35 in a 2012 Nissan Juke
Yes the Optima is a spiral wound AGM, the focal point was it took a charge and held it, where the conventional batteries had a measurable loss daily. In each rig!

I'm unsure if these are recycled, there's nothing indicating they were, but the performance is dismal, I suspect they were "reconditioned"  (not re smelted or even significantly rebuilt ( I suspect the had the case cut and any particulate flushed out and then the case rejoined)) and sold as new. One was picked up at NAPA and the other at Oreilly's, the 35 was from Les Schwab Tires (I dunno whom their supplier is).
I attempted to return the NAPA one, they ran tests and said everything was in good working order and tried to sell me a new starter, telling me "probably my starter was worn and taking inordinate amperage" On one vehicle I could believe it, on three I doubt it,
Even without attempting to start the vehicle the amperage drop is simply a function of time.

In the Dodge were both batteries replaced at the same time?

2 separate Dodges,
batteries replaced about three months apart