This sandbox you speak: does it given enough effort grant everyone the ability to make the same superior products you talked about? If so, how is that different what you are complaining about here? Once you have reached the top tier, the stuff you make is no better than the stuff from the next guy. A sandbox as you describe is will not be much of a gate because player will eventually just grind through it.

You are from a smaller server, so was I back in the beginning. While I was there, I was one of a very small number of crafters had the Master Book II recipes unlocked. Those book unlocks were pretty difficult and this led to a situation similar to what you are talking about SwG. Very little competition because a small oligopoly controlled the high end market. In larger scales economies this becomes irrelevant because your competition pool is larger. Also, in Heavensward the requirements for those master recipes became trivial and gating was done with Specialization.

About undercutting... you know the system is not that good when is your only option to compete with other players.
So you are saying that RL stores put products on sale for a different reason? There only four reasons I know of:
1. To be a lost leader to generate foot traffic for other products. [this has almost no applicability in this game because we do not have our own stores in this game; which would be a neat idea but it would suffer the same problems Ul'dah's market does. Wrong location, very limited traffic, and many players upset]
2. To undercut the competition
3. To clear inventory before it becomes a loss (e.g. produce going bad) [consumables from a couple patches ago would apply here; I used to make a Cockatrice Meatballs, now you can barely give them away]
4. To clear inventory space before new products arrive [our overloaded retainers]

For a time in early HW, some items like Dravanian Mistletoe were only available from gathering, this lead very high prices for base items. SE then made these items available for purchase from a vendor. After that, the price on MB has pretty much always been lower than the vendor price. All the non-player competition did was lower the price. All other factors and behaviours remained the same. If you are not competing against other players, who should you compete against?