The time management i agree with, as i have personally sold over 6+ emps for gil. However, the prices are high for briareus. I charge 500k per apademak horn, glav shell, chloris bud, and those are NMs that require a bit more work for pops/ or time to kill.
Charging people for time is the stupid part here, never in my 400m + in orders have i charged anyone for time. If he was smart, he would have them come along and hold pops for him to speed it up, not try to charge them for time.
500k for bria is high, very high, that being said, farming an emp for someone is still work, and i wouldnt take under 300k a pop, do 350 and its probably reasonably priced and a fair deal for the buyer, as well as profitable still for the seller. Once you get to sobek, who is as easy, just a bit more competition on guku, up it to 400k or so.
Guess you can charge what you want, but just a heads up, you are not the first one to try/do this, so dont be shocked of nobody wants to pay 500k+ for items that others will sell for less.
***, i've dealt with a few people who hardly had stones when abyssea was fairly new, and i had the pops pre farmed so they could just zone in and lot. If your prices dont keep people away, your ***service will