Note: Since this is a huge issue in FFXIV this will be a long explanation and in depth, so that SE may take it to heart. Therefore if your one of those tl;dr derps, dont bother wasting my time.
There's another thread out there that says the same thing, bless the OP's heart, but he didn't explain it very well for those who don't know.
Problem right now:
The problem right now is that its so easy to under cut, and the undercutting is happening when it really shouldn't be at all. Some crafts feel this far worse than others, but regardless of whether your ignorant to the problem or not, everyone is forced to deal with it.
The reason its happening is because the only real window you see is what everything is currently being sold at. The "History" window is something not many people use from what I've been able to tell. Coupled with the problem that people just throw stuff up "just to sell it". Then more and more people sell it at that price, because they have too, or it simply won't sell.
This is amplified 10x worse by the fact that the game jams equipment down your throat left and right by simple and easy quests even at lvl 50.
People who like to craft, and spend their time gathering and crafting deserve a system which doesn't punish them. They deserve to be able to sell their goods at a fair price, without having to be worried about getting undercut by 60% and or selling at extremely low and ridiculous prices.
The Fix:
The fix would be to create a market board that works like the AH in FFXI. This was a perfectly fine tuned and incredibly efficient way of making prices both solid, yet still fluctuate.
How it works.
Basically it shows the last 10 sold at prices. Nothing else.
Lets say for an example with made up prices, that your buying a Cobalt Cuirass.
You go to the market Board, look up the item, and the prices are as followed.
5,000 5,000 6,000 7,000 7,000 6,000 5,000 5,000
With 3 being sold currently. What you Don't know is that 3 being sold at are
7,000 8,000 1,000
So you bid at 5,000 since that's the lowest it seems to be sold for. You get the 1,000 item at 5,000. (not 1,000). The person who put it up for 1,000 gets 5,000 and you get the cobalt item. Your buying price of 5,000 gets tacked into the last bought prices.
Another person goes to buy one right after you, Bids again for 5,000, doesn't get anything. He bids again at 6,000, still doesn't get anything. So he thinks "is it worth going to 7,000 for?" Decides it is, and bids at 7,000 and gets the item selling at 7,000. In which case his new bought item price is tacked to the board.
The new prices are as shown for Cobalt Cuirass: Other prices Your price you bought it at The other persons price after you
7,000 5,000 5,000 5,000 6,000 7,000 7,000 6,000
So what does this do?
Going off of the "things are only worth what people will buy them for" is absolutely right, and should be exactly what it is. Right now its "Prices are only worth how few people are undercutting it by". Which isn't how it should be. You decided what its worth by bidding for it at 5,000. If too few people are buying it at a set amount its up to the seller to lower the price, where when they hit the level that people are bidding at it for, will start to sell them like hot cakes.
This keeps prices fair and stable. It allows both for the Sellers, AND buyers to decide how much items are worth. You decided when buying it that its worth 5,000 or you were WILLING to buy it at that price, and therefore you got it at the price. This makes it so crafters as well are not constantly hampered and under cut by people who get equipment for free through quests, or just to get rid of it. As even the person who put up the Cobalt Cuirass for 1,000 gil, still didn't under cut the market, and the crafters are still able to sell their items at 5,000.
Furthermore, when people go to sell items, they see what its being bought at. Not what others are selling it at. This makes it much easier for people to see items being sold consistently at 5,000 to put their items up for 5,000 knowing that it will sell at that price.
Conclusion:
The conclusion is that as the market stands at the moment, the undercutting is way out of control, with people undercutting for no reason, making crafting just about useless, except for materia melding. It's creating a chaotic market that is pinching crafters choices and forcing them to make only specific items that not many people are making to get a fair price.
The bottom line is crafters deserve to get a fair bid on their items, and they deserve to not be undercut 100x and forced to sell their items much less than what they are worth. Crafters also deserve a balanced market, where both sellers and buyers decide on a price, not how much its being undercut by.