I sort of lost track of the original question, and wrote about stuff you didn’t ask about, so hopefully you don't mind reading about other stuff with regards to FUT;
It is worth explaining the difference between coins and fifa points.
fifa points are like scratchcard credits that you can purchase with real money and it gives you a right to open packs. Think of having a credit that you can only open packs that are only provided by EA and you can't buy players/cards with these points. How on earth this fifa points scheme is not considered gambling I don't know.
Coins on the other hand, can be treated as currency I guess; you can open EA packs or purchase players from the market.
From EA's point of view, purchasing packs with coins doesn't earn them any money. They only make money when you open packs with fifa points (and they make a lot of money from UT franchise in general, see this; EA’s Ultimate Team services generated more than $380 million* in fiscal year 2014, with Madden Ultimate Team growing 90% year-over-year.
People prefer coins because they are much more flexible and can be earned for "free" by playing the game, and you can purchase players/cards directly from the market and (maybe not in the beginning but) over time coins are much more cheaper than fifa points if you purchase them from coinsellers (as in, for the same monetary value, you can open more packs with coins than points).
So how do coins enter the FUT economy?
There are two ways coins enter the FUT economy.
1) Playing games (after which EA awards you Fifa 16 coins).
2) Discarding packs.
I'm not including selling cards on the market because when you sell, you are getting coins that are already in the FUT economy (as in from another user), not EA.
Well, alright, the more you play FUT matches, more coins you earn. If you win games, you earn more coins, and if you win titles, you get a coin award. So winning is awarded with coins (and sometimes in addition to coins with packs too).
Also If you open packs you have the option to "discard" cards after which EA gives you a small amount of coins. For example last year, if you discarded a 75 rated rare gold player, EA gave you 600 coins. It might not sound much but if you open a lot of packs, and can afford to just discard the whole pack (because maybe it was completely useless), you could make around 1500-2000 coins per pack (this is standard gold pack). Alternatively you can list items individually and make more coins.
The market works as an auction house, think of ebay for example. But the auction rules are a bit different, participants bid openly against one another, with each subsequent bid required to be higher than the previous bid (this was from wikipedia english auction description).
The seller needs to specify an end time for the auction. The seller can also put a buy it now price and needs to set a starting price. When the auction is in its last 30 seconds and if there is a new bid, the clock adds another 30 seconds to give other bidders a chance to bid again ( I might be slightly wrong about the added time, feel free to comment and correct me). As you can guess, if the player/card popular, the auction could prolong for a bit while increasing in value.
The market I think where EA faced some problems in the last couple of years where users started abusing the market with the intention of making coins and then selling it for money.
For example, people used “bots” to scan the market for players with undermarket valuation and snapped them and then put them back on with Fifa 16 coins pc. I don't have any evidence but I think people used this scheme to set prices of players as well (as in price fixing).
Another point worth explaining is the so-called EA tax. As a seller, when you make a sale, EA takes a %5 cut of the sale value. Some people don’t like this but I think it is a good way of regulating the market. If there was no EA tax, you could inflate the prices of players since you could game the system. To give an example, suppose you listed a player, and someone bid. You could in turn from a different account bid on the same player. If the other user bids again, well you are in luck, you just managed to increase your return on your listing for no good reason. If the other user doesn't bid, you'll win the player with no loss. EA tax gets rid of this kind of behaviour in the market.