Sometimes I take my chances, leave an aircraft for sale at 70%, and sometimes I get lucky.
Perhaps another option might be useful: being able to lower price below 70% of value, and the lower the price, the higher the probability of broker (or a player) buying, but again, you are taking your chances, and it will take time.
The only sure thing should be the scrap price, that happens immediately.
Yes, after ~24-48 RL hours on the market the minimum price allowed drops to 30% of calculated value. I also agree with LemonButt...in real life, there would be airlines looking to source DC-9's in the mid 90's, 737 classics even now, and so on and so forth. The problem is, those airlines are not in AWS. Even what would be considered "third world" airlines IRL are operating new Boeings and Airbii in AWS. So in the real world, there would be SOME demand for "undesirable" aircraft driving a percentage of quality discarded to the brokers.
So, how about this. Instead of making he brokers buy all our unwanted planes, add a second AI buyer: the parts broker. There is a significant difference between the parts value of an asset and the scrap value of the same asset. If the scrap value is 20% of the value of the plane, maybe make the parts value 40-50% of the market value and make the parts broker obtain a reasonable inventory of parts aircraft in relation to the number of a type of aircraft in service/storage. This would not be an open market transaction, but rather similar to the scrap function. A player could choose to sell the plane to a parts broker, and if the demand was there for the type being offered, the broker would pay the predetermined % of the frames value on the spot. If no demand for the type existed, the broker would refuse the plane. If the parts broker refused the plane, the scrap function would immediately become available for that frame.