One thing this doesn't take into account is the price for each, the size in stacks of other mats, how fast they are selling, other servers economies, undercutters, and items farmed, shared, and sold across multiple accounts with multiple retainers. It also doesn't take into account that the RMTs are farming everything under the sun. If shards were the only thing truly profitable any everything else is a waste of time, why would they bother farming anything else. That reason alone supports the "They would move on to something else" logic that both Hvinire and I brought up.
Increasing the amount of shards that can be acquired will have little influence on RMTs, as they are scoring on all profitable mats.