I think it is possible to incentivize sellers to increase market liquidity(amount of cards selling).
I'm currently an undergraduate student in economics at my university, and I tried to model the auction market using a simple agent-based model:
If you think about the seller point of view, he has to think about two things:
- The expected return of putting a card to sale
- The hassle of putting a card to sale
To reduce the hassle to sell a card not much could be done. The gold cost is already negligible. On the expected return from putting a card to sale, there are two things:
- The probability of making a sell per unit of time
- The time the order is in the auction house
At a given price, the probability of making a sell per unit of time is roughly:
(the amount of people buying per unit of time) / (total of orders in the market)
A way to increase this would be increasing the number of buyers(or players), but it is not something trivial in the short run.
The easier option would be to increase the time of the order in de AH.
In the end the formula looks like this:
Expected_value_making_order = (amount_of_buyers/amount_of_sell_orders)*(time_in_the_AH) - (hassle_of_making_a_order)
If the set time in the AH is increased, the model predicts that the amount of sell orders will increase until the expected value of making the order reaches an equilibrium. So, in essence, a doubling in the time of the order, for example, would result in a double in market liquidity.
Another point is that when the number of buyers decreases, the market loses liquidity. It is possible that when players start completing their decks, they, on average, buy less cards, driving market liquidity down.