The suspension jassi refers to is here https://deckbox.org/forum/viewtopic.php?id=22970
It also has nothing to do with tcgplayer or with trying to monetize the website, i'm not sure how you got to that conclusion.
That user clearly tried to take advantage of market price fluctuations and deckbox bugs to abuse other users via the trade system, so he was suspended.
It also has nothing to do with buying and selling, and could have happened very well even if our prices were not based on our market, but on some other external source. Prices were many times off when we got them from tcgplayer too.
Like in any kind of partly protected system, we here want to protect our users from abuse. In that case 20 people were just about to lose 10$ each, due to a fluctuation that deckbox prices did not respond to (so a deckbox bug you can say), and a guy who thought he's entitled to steal that value because he noticed the bug. Also he did not bother to tell us about it when he saw it, instead he opened 20 trades with people who did not know the price spiked 2 days before.
The case referenced before is not about marginal arbitrage. The card was mistakenly marked on deckbox as being three times less expensive than 90% of all other websites - ebay, tcgplayer, amazon, star city games, adventureson, all of them, with a 10$ difference on a 5$ card.
I'm not yet sure what the solution to this problem is, or how to phrase a rule that clearly explains what is abuse. But I still stand very decided that arbitrage of that sort on market fluctuations is pretty clearly abuse. Preventing that is of course not an easy problem to solve, but I would still like to prevent it. Until we have a good solution, suspending people who blatantly do it is a temporary one.
Feedback is as always welcome on the topic. I do not want to ignore the problem.