Okay, so with the new IM update we finally have an item that can be bought with in-game currency and with real money. That item is the scrolls.
Let's take for example Warrior's Scroll I: Melee Attack that costs ~50RP, when bought with RP, and 2 Insignias, when bought with in-game currency.
Lets do the math:
10$ = 1000RP ; thereore 50RP is worth 0.50$
since 50RP is worth 50 cents ; 1 insignia = 0.25$
Here is the math on some of the items:
Paying 5 insignias for a Sedorian is worth 1.25$
Buying a lvl 66 weapon with insignias is worth exactly 10$ or 1000RP
Any endgame ring that is worth 1500 insignias can cost you up to the equivalent of 375$.
You just spent 20$ on a lvl 60 ring that gives exp bonus 8% and portal cost reduction 12%
Each day when you login for after a week you receive 0.50$ worth of Insignias
Sometimes you can find 0.25$ when you kill mobs
Ofcourse this is just speculative since most of the costs in Rohan are not well represented and prices vary, ex: 1 Hour monkey costs 4 insignias while 7 days monkey in IM costs 150 rps which equals to 168 1 hour monkeys = 150/(168x(1/4)) = 1rps is worth 0.2232 insignias.
I would prefer to go with the 1st variant of calculations, although it may seem like an overprice, it triumphs over the 2nd example, since the items in question are both identical not only in name, but in length.