Coin selling requires the ability to find a specific card on the market. There are 4 possible steps in order to make the market as obscure as possible.
Step 1: remove club names from cards on the transfer market. this is suggested a lot but people always mention that you could list a card for an obscure price and find that. so for the next steps
Step 2: Whenever someone lists a card worth more then 10X worth it's lowest BIN, EA lists a dummy card for the same price. If EA could do this, coin selling would be DONE, and step 3 and 4 would be unneeded. If EA can't do this, then they can do steps 3 and 4. Edit: Upon further thought, EA should just no allow listings for players 10X over the lowest BIN.
Step 3: make it so you can only bid with numbers that have 2 significant figures, and the last digit must be 0 or 5. so you could bid at 900, 950, 9000, 9500, 50000, 55000, ect. This would make it harder to list cards at obscure numbers. If that isn't enough, make it so you can only bid to 1 significant figure. "But wait, this ruins trading!" you know what ruins trading? coin selling.
Step 4: Cap non rare bronze cards at 10k, non rare silvers at 15k, and non rare golds at 20k. Cap rare bronze cards at 50k, rare silvers at 100k, and rare golds at 15 million. if people have to list rare gold cards to buy Fifa 16 coins, It means their cards are more likely to overlap with other people listing rare gold cards at weird prices, and there are plenty of weirdos doing this already.