I actually think the RMTs work mainly with the crystal wards, low cost over head, just need fishing and alchemy and you can fish for all the ingredients you need. which means you can sell them for pretty low and still make a million gil in a few days. The retainers that might belong to RMTs are the ones that throw up 10 stacks of 999 crystals (all the same element) at once and leave it alone for about a week or two even. If you don't want to do business with them don't buy the crystals off those retainers.