Chronoscrolls/PLEX do favor people with a disposable income, but it also makes it so people without a disposable income can theoretically play for "free/gil". It has worked in other games... perhaps a limit on how many Sub Replacement Items one can buy per 30 days... eliminate normal subs, cap it at 4, so Buyer uses one for himself and has 3 to sell.

It's kinda like speculating on Gil Futures, $9.99USD = ?? Gil.