Getting back to this topic. I agree. Do not change Isle of Souls drop rates/amount, or special adena boost skill. If anything, give us more mobs there and make other instances as lucrative, perhaps through drops of rare items.
Anyway, I finally decided to test out IOS to see what I could earn. I bought max IOS Recharges. I already had drop rate/amount runes in my inventory. Unfortunately, I only have one character that is high enough level to enter the zone. I entered with only 1M adena in my pocket, leaving most of my adena in WH.
Results? After full max recharge time was expended I was able to make 4.8B adena. I probably could have earned more if I picked a different spot where more mobs spawned.
It goes without saying, if I had other characters that were 107, I would send them there, too, to maximize earnings. I'm not greedy. I'm already "rich". I'd be ok with making just ~5B a day in IOS. But if I was like other diehard gamers with squads of well-geared toons over 107, yeah, I could easily see them earning 20B a day or more.
Some say having a few players with that kind of income ruins the market. I disagree. What ruins the market is rarity of items combined with very greedy market players. Surpluses usually drive prices down, curtailing demand...except when you factor in L2 sellers, who usually overprice things from the beginning. L2 players are the worst. Many of them would probably find themselves in court for unfair business practices, if not in jail.