You're only on the hook for certain bonuses. Roster bonuses get paid out when the player is on the roster, signing bonus is due at signing, workout bonus gets paid out when they fulfill the requirements, etc. Playtime incentives, stat incentives, all of that.
While all these count to some degree against the cap in terms of dead money, and would count in cap dollars - this money isn't necessarily paid out if the players don't fulfill the requirements.
The Patriots have been notorious for cutting players right before they have to pay out big bonuses, or artificially reducing playtime so players don't reach bonuses.
Rhamondre Stevenson played 0 snaps last weekend. He was just short of 1000 yards. Do you think maybe he had a bonus for hitting 1000 yards?