In my humble opinion, exex is broken because it offers the best price with 0 work on anyone's part. You just look at the number, and price yours higher or lower depending on if you're buying or selling.
Undercutting is a huge issue, that not many truly understand. There are still people who will argue with me over "lower prices helps the newbies", which in fact it does not.
Let's look at a classic example. Archery 120. Arguably one of the most valuable scrolls on the server.
If it's going value is 3 million gold, you need to sell 9 of them to purchase a relayer, at 25,000,000 gold. If people keep undercutting it, and the value drops to 1 million gold, now you need to sell 25 of them to get that same relayer. You've just forced the new player to work 3 times harder, to get the same "value" out of their work. They need to do 3x the champions, because the scrolls have been devalued.
In your example, a difference of 500k - 9 to buy a relayer vs 10. Not a huge difference, but a difference none-the-less, with that person having to work harder to get the same end goal.
It's a quick fix, and instant gratification that rules the day, but in the end, it takes them more to catch up than the guy who waited and sold the item at the actual value set by the market.
As a guy, when I know I'm after something in particular, I'd rather not have to sift through 20 different listings to find the best deal
That's why you pay more - for the convenience of not bargain hunting.
SWG isn't really comparable to UO, because the crafting was so different. Two of the "same" item could have vastly different values depending on the materials used to make them, and/or how the stats rolled. Here, batwings are the same if you loot them, or buy them for the 47th time from a player. They also don't degrade, and have a limited lifespan as on SWG.
Another example is "I mined it, so it's free". While technically true, what most people fail to consider is what those ingots are worth. If you go mine 1000 ingots, and you can get 8000 gold for them, that's what you're losing out on, regardless that you spent the time to mine them youself. You could have 8000 gold (by just selling them), or whatever you make with those ingots. There's an opportunity cost involved.
Lets say the going rate of iron ingots is 11 gold. You decide to undercut the next guy, and put yours on market for 10 gold. 1st guy needs to sell 2,272,728 to have 25 mil, you need to sell 2,500,000. Not sure how long it takes you to mine up an additional 227,272 ingots, but you're working that much harder by undercutting.
Granted rune books make that much easier, but I do miss going to people's houses ( I guess tents are gone) and buying because they were actively encouraging people to visit...ahh the days of those xroads and cove vendors 
