I just had an absolutely random idea that I decided to share here. Not because I think it will be used by the developers, but because I think this is a real 'million dollars idea' and it is just a matter of time before someone will use it in conjunction with a digital TCG.
Three weeks ago Steam Dev Days 2016 happened, and for a number of reasons one particular video from this event has caught my attention. This video: https://www.youtube.com/watch?v=jDfhPTSOLis
Valve tries to create an additional level of monetization for the developers through significant improvements and expanding of Steam Marketplace. Developer of any game can use Steam API to add in-game items that can be given in the game, but traded or sold through Steam.
And my random thought is that it's an ideal solution for a digital TCG that wants to have trading, real money trading, and an auction house. Merge your game with Steam, duplicate every card that players receive as a Steam item that they can sell or trade through the Steam Marketplace. All these deals are protected by Steam, developers (and Valve of course) have their cut from each deal, and if you look at games like Counter Strike or Dota 2, they have thousands, if not millions deals every single day! Here is the income for the developer, isn't it?
And the system works in a way that the players themselves adjust the prices because Steam Marketplace works as a giant auction house. Have an unique or nearly unique card? Be free to charge $100 for it. Or sell thousands of your commons for 5 cents each.
Plus the visibility at the Marketplace is a promotion for the game on its own, at least at this stage, because not so many developers use this feature right now. It's something about 30-40 games.
LM won't do this, this is way too much work for them, plus they don't like the very idea of dependency from Steam, but I think the first TCG that will use this system, had a real chance to caught attention of millions players who use Marketplace. And the genre itself is perfect for this system: sell boosters for direct income, duplicate cards as Steam items, allow players trade their cards away and spend the money to buy even more boosters. If people buy freaking skins for their guns or other purely cosmetic stuff, I'm sure they will gladly pay for something that they actually can use to play, i.e. cards. And if this isn't a fastest and cheapest way for new players to find and buy cards they need, I don't know what else it might be.