You'd have to account for higher Chaos dungeon tiers. The modifier for a chaos dungeon at 1340 is 140%, and the modifier for a 1370 is 200%, which is 42.5% more mats from chaos at 1370 compared to 1340.

While you might have approximated some value to the guardian/destruction stones, you must also approximate some value for the extra silver, extra shards and the fact that those will drop bound great leaps compared to normal leaps. Among other factors.

you also need to factor in the Argos blood, and not simply the raw gold you get from both hardmode and Argos. Since both Argos blood and Oreha's empyrean dismantle into bound great leaps (at a rate of 1x per empyrean and 2.5x per blood)

- Another factor which you didn't include is the 1370 honing nerf. So advising people to push their alts to 1370, when it in fact can get nerfed (rather heavily I might add) is irresponsible.

The honing nerf changes the average leapstone cost from around 700 for 1340-1370 to only 200, among other factors dropping significantly in cost as well. So it will likely be about 1/3 or 1/4 of the cost to push alts post nerf as compared to pre-nerf.

When this honing nerf will come is anyone's guess. But if it were to come with Valtan, which would be worst case scenario for your advice, then this would obviously be something that changes the advise you were to give.

However, we do know that the honing nerf only affects -1370 and not past that. Therefore, we have some knowledge some certainties, mainly pushing past 1370 is more of a constant than pushing alts to 1370 itself.

all in all, I highly disagree with calculating an ROI based on sellable materials alone. A true ROI would include both bound and unbound materials, as eventually pushing alts higher should be part of the gameplan.