Cash Shop: Where do you draw the line?

[Ultimatecalibur]

And when it becomes unprofitable for the RMT, the number of buyers will dry up (because far fewer people have 20 mill gil than 5 mill gil) which brings the price down again, which makes it profitable for RMT again.

And then SE introduces a new cash shop item that can be traded and the market spikes again.

All the while, more gil is entering the market, raising prices again.

That sounds true until you realize that the cash shop item sellers are those that would normally be RMT buyers. The system ends up killing RMTs because they end up competing with their own customer base. Every player selling cash shop items is someone who might have purchased gil from an RMT.