You listed Over The Cap's numbers if the Seahawks cut Lockett. They have different once for when he's traded though.
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There's a huge difference whether the Seahawks already paid him an option bonus of $13 million (that would result in dead money counting against Seattle's cap if he's traded) or he's due a $3.25 million per game roster bonus for each of the next four seasons (the team acquiring him would take that cap hit with no dead money resulting out of it for the Seahawks).
If he's traded before the start of this season the base salary of $3 million will be fully paid by the acquiring him, therefore that would definitely not result in any dead money for Seattle.
You don't fully understand the concept of dead money counting against the cap.
Most importantly, there are two scenarios which could result in a different amount of dead money counting against a team's cap in a player either being released or traded.
If a player is released the move will result in all money already having been paid to a player but not yet accounted for in the salary cap (remaining prorated portion of any bonuses)
as well as all future guarantees counting against the cap in dead money.
If a player is traded the team acquiring him will take over those future guarantees resulting in less dead mone for the team trading him.
If Spotrac is right about the option bonus there's no way the Seahawks are interested in trading Lockett.
The base salary of $3 million would be paid by the team acquiring him and wouldn't count as dead money against the Seahawks cap.