If they're signing as a starter it's up near $20.
But idk who these $5m players are, even with the cap manipulation, that's not what quality players cost. These 4 defensive - presumably starters - players who you get for $20m do not exist. Those who come in at that price range are not good players. Brown, for instance, is a rotational role player. You're basically saying that you'd trade Dak for Andy Dalton, Anthony Brown, Malcom Brown, Duron Harmon and Kyler Fackrell. Or you could do Jameis, Patrick Robinson, Shawn Williams and Denzel Perryman. Either way, your defense still sucks and now your quarterback sucks too lol.
At some point you need to do the leg work to understand what players actually make.