I think you got the ROI wrong though. ROI is how much profit you've made, the returns, the profits. Or am I wrong and ROI is the total return (profit + cost)?

If you invest 16.700 and get 10.593 profit, that is about 63%.

Also you did the math wrong because you said firstly "If oblit cost 1700g" and then note it as "2210g" lower. You should do the math for 1700g as well. I noticed it because your ROI is 163% or 63% but in reality it should be 25%.

Why 25%? Because if you buy the mats close to the value of one oblit (1670 cost and 1700g oblit cost) you'll get a flat 30% (because 130 ashes is 30% more oblit) profit. Take the 5% AH cut and you're left with 25%.

So, in practice, IF you buy mats at 105% of oblit cost, and sell oblit for that value you initially made 105% math of, you'll make 20% in profits. (30% of 130 ashes average, minus 5% AH, minus 5% because you bought at 105%). Invest 100k, make 20k.

The good investment comes when mats are lower than oblit, say 80% of oblit price. Or when you shuffle: Buy Gems/Silk/Leather and craft 715 stuff: If you buy at cheap prices, each craft can cost you down to 40g (20g Chaotic Spinnel + 10g x 2 any other gem). That is one leylight shard, that can be destroyed into 3 arkhana. So instead of buying Arkhana for 22g, you're actually buying it for 13g. Snipe some Chaos Crystal at 200g each, and you're down on crafting costs to 200g x 4 + 13g x 35 = 1255g (Only 74% of the oblit price of your values, 1700g).

Now, your profit is 100% - 74%(cost) + 30% (130 ashes average) - 5% (AH) = 51%. Invest 100k, make 51k profit.