You don't need lvl 70+ in order to use non-SIB weapons to good effect.
loosely, my considered opinions on this are:
1/ This stuff is very hard to define, expensive to test, subject to huge swings in general loot, affected by your historical losses etc
2/ Everyone has their own opinion
3/ My opinion is that I agree with JC, to a certain extent
...but...
4/ Most of the time I use (L) maxed
especially for bigger mobs
5/ I've found that a weapon-set with, for example, half the "eco", (therefore twice the "decay") does not give a long-term return the same level of loot as the control (L) weapon.(TT loot return) it gives somewhat
more, with longterm useage, suggesting an `somewhat` automated avatar-based loot return system. It takes quite some time to re-adjust.
6/ more losses "into" a mob (eg: due to lower DPS so higher regen during time to kill) affect loot output `somewhat`, and item drops to a small extent (changes in types of oils looted etc)
7/ That `somewhat` varies hunt/hunt, day/day, week/week, month/month.
8/ Most people can't afford to test enough to give a large enough data set.
5000US$ is a reasonable input to test with, 100$ is certainly not.
9/ Wide-scale long-term multiple avatar studies would be needed to fully test
10/ For comparisons, only weapon-sets
very closely matched in average damage per second are valid. eg: k400+a104, cb19+beast are similar on low-level mobs. (where a high enough evader prof negates advantage of 1 or 2 extra shots before tanking) but comparing that level of damage per second with a Kat. Det. at prof lvl 50 damage and hit is NOT acceptable (at a guess, it's about 10% underpowered?) so fap/armor decay is 10% more (with a blade, it's up close all the time) that will skew loot results by an unknown factor, not necessarily 10%
11/ Market "interests" skew opinions
12/ I believe that your PED outputs are broadly linked to your PED inputs
eg: 1000$ in, 900$ out, over a given "time of play". Cycle that again, and you get 90% return again, and so on, until you go broke.
I have my own anecdotal evidence to suggest this was
not so rigid in years gone by.
13/ Various things affect uber loots, like: pure luck, time/place, tactics, past financial profile (in/out/spend/retention), public relations potential, and the infamous alleged "favoritism".
14/ Hunting wisely with good eco weapons seems to be far risky in the short term. Meaning: using non-L with low skills means you'll be consistently needing to depo more to keep going. It's not as bad as some people would have you think, but I'd recommend (L) until at least level 55-60.
15/ Using plain "eco" figures, some (L) weapons are better than many non-L ones even at level 90+. Eco is not the
whole story; especially if you have, let's say, 20,000US$ to depo, it's largely irrelevant
16/ Skills gained should be viewed as "loot". Their amount varies greatly with the choice of weapon, in my experience.
Note: I don't research this stuff like I used to.
I've lost interest in the game the last year or so due to depressing returns and almost no markup items worth selling. Even an ATH wouldn't get me back on the level an more, it's been that bad in my experience. Ymmv.
I own various L, UnlimL (cheap ones) and non-L (oldskool) weapons. I'm past caring these days. My pedcard is always near zero. No-one reads this stuff much anyways.