You trade the contract and the control, not the player.
The asset as contract and control, prospects as currency, and the two-sided deadline market.
The asset is the contract and the control.
In a closed league you do not trade a player, you trade his contract and his control. So the engine prices a tradeable player as his surplus: his projected win value minus his salary across his remaining control years. A cost-controlled young star is worth far more in trade than a better player on an expiring or above-market deal, because the control, not the raw talent, is the asset.
The controlled young star projects $20M of value against a $4M salary for four years, a $64M surplus, while the equally-good veteran on a one-year above-market deal carries near-zero surplus. The engine prices the contract and the control, so equal talent on different deals is very different trade value. You trade the contract and the control, so a controlled young star outvalues a better veteran on an expiring deal.
Illustrative engine read on the real trade-value-as-surplus (projected win value minus salary over the remaining control years, equal talent on different contracts shown as different trade value). Composite players, demonstration figures flagged v0 and current-as-of.
Prospects as the currency.
Prospects are packaged future control: six-plus years of cost-controlled team control at a wide amateur-to-pro projection band. The engine prices a prospect package as the surplus it projects to generate, discounted by its bust risk and the developmental runway. A contending team spends future control to buy present surplus, and both sides are priced in the same currency.
A prospect package projects $70M of surplus if it hits, but bust risk and the developmental runway discount it to about $22M of expected surplus at a wide band, and that risk-adjusted number is what a contender spends to buy a present star. Prospects are future control, priced in the same currency as present surplus. Prospects are packaged future control, priced as bust-discounted surplus in the same currency as a present star.
Illustrative engine read on the real prospect-as-currency pricing (six-plus years of control at a wide Mode 6 band, discounted by bust risk and developmental runway, exchanged for present surplus). Composite package, demonstration figures flagged v0 and current-as-of.
Both teams must gain.
A trade clears only when each side gains surplus given its own window. A contender values present wins, a rebuilder values future control, so the same player is worth more to one than the other, and the gap between those two valuations is what makes the deal.
The same controlled star is worth a win-now to the contender and a package of future control to the rebuilder, and the deal lives in that gap, with the tax on money taken back, the deadline pressure, and the 40-man consequences all folded in. The engine prices both windows, because a trade needs both sides to gain. A trade happens only when both sides gain surplus in their own window, and the deal is the gap between them.
Illustrative engine read on the real two-sided market (each team's window valuation, the surplus gap that makes the deal, the CBT on salary taken back, the deadline, and the 40-man consequences). Composite teams, demonstration figures flagged v0 and current-as-of.
The engine finds the deal in the gap between what a player is worth to a contender and to a rebuilder.
Price the surplus. Find the gap.
Trades price the contract and the control as surplus, read prospects as bust-discounted future control in the same currency, and find the deal in the gap between a contender's window and a rebuilder's, with the tax, the deadline, and the 40-man consequences folded in.