One has to look at the actual cost to produce.
The present rate of 16:4:1 is correct when only weighing the cost in gold and supplies, which happen to be the ones that are the easiest to collect and thus are of least importance. But for those the cost is pretty much in accordance with the present ratio
The real problem is in the amount of space, pop and culture needed to produce a comparable amount of goods. So I'm looking at my factories, all same level, all same boost (700% relics, 100% from the Mountain Halls)
Lvl 27 steel : 3960/3hours on 4x5, 6529 pop, 1690 culture.
Lvl 27 scrolls: 4860/3hours on 4x6, 10968 pop, 3499 culture
Lvl 27 dust : 5040/3hours on 5x5, 13057 pop, 4165 culture
So per square production is 198 : 202,5 : 201.6 which is well within reasonable comparison rates, with T1 being the lowest of the lot.
And the requirements per square are
pop requirement ratio 326,45 : 457 : 522.28, or 1 : 1.40 : 1.60
culture requirement ratio 84,5 : 145,79 : 166,6, or 1 : 1.72 : 1.97
So PER SQUARE, T2 goods only require less than twice as much culture as T1, which is not even close to the ratio of 4:1, with T3 needing only about 2x as T1, which makes that waaaay out of sync.
The pop requirement is much, much worse, neither coming even close to the present in-game ratio, with a T3 factory at lvl 27 requiring only about 1,6 x as much pop per square as a T1 factory, but the production is 16x the value! A ratio that is 10x out of proportion.
Now I get the idea that higher tier goods can't be 16x as expensive, but right now it is horribly inefficient to produce the T1 goods as their requirements in pop and culture are way higher, meaning they need much more space in supporting buildings to provide that pop and culture, which is why we see so many cross-tier trades all over the board.
To fix this 9:3:1 would already be much closer to the real rate, though when looking at the extra amount of space needed in pop and culture to maintain the T1 factories 4:2:1 probably is even closer to the truth.
Another solution may be to combine the data: change the rate to 9:3:1 AND increase the output of T1 factories by a lot and the T2 by a bit to compensate for the extra support buildings needed. That however would require much more calculation and will generate much more discontent from players than just changing the ratio.
Another option is to take a look at how much pop and culture will be needed for the different factories and make an adjustment there. (Especially considering the really incredibly ridiculous requirement on the amount of pop needed to upgrade the T1 factories to lvl 28-32, the amount of pop needed to upgrade these factories is completely insane when measured against the increase in output).
But with the present per square requirements, the ratio would be close to something like 4:3:2, though one should figure in the ratio of gold and supplies, so perhaps 5:3:1 would be reasonable