That's a good way of doing it but it's not going to get you to 50 because to go from 30 to 50 you're looking at about 4000 synths. How long do you think it will take you to sell 4000 profitable items or 1333 stacks of arrows? If everyone tried to do what you do the cost of arrows would be about 5k gil a stack and us archers would be very happy.
You don't lose much gil on masks anyway, CRP is probably the cheapest craft to rank up. A walnut mask sells for about 1500 gil to an NPC, you can buy a log for 8k so that's what, 500 gil loss per synth plus shards. 4k synths is 2mil gil. Hardly worth going into the kind of effort you are to skill up. If you make the shards yourself from fish and crystals you can do that cheap too. There's faster ways of recovering that 2mil + shard cost than doing what you're doing. Like getting to 50 sometime before next year and HQing crab bows. :P All those items you can HQ at 50 are losing value the longer it takes you to get there. You're losing gil there.
Does your customer have a screen outside your shop telling you what your price is, your neighbour's price is and every other shop in the city's price is? No? Then don't compare it to the real world. I believe I covered this already.
People are clearly missing the point/unable to read in this thread. Coming out with tripe like "if someone can sell their product cheaper than you then they should" because this isn't about selling it cheaper, it's about moving your product first. Do people honestly care about the 1k gil they lose from undercutting a stack of 10k items by 10 gil? Do you honestly believe they're undercutting because of price? Yet half this thread seems to think yes.
No, they're undercutting because they want their name at the top of the list in the same way a child always wants to go first. Their name will always be at the top of the list, because selling it for 10 gil less than whatever you list it at is irrelevant to them. I have started to combat the issue somewhat however. My alt character is almost always sat by the market wards when my main is out on the field.