The is no way to know whether we overpaid now. What we do know is that Ainge exchanged one highly problematic asset(IT), one valuable and stable asset and two highly variable assets for one elite player that is a much safer bet, and most importantly, fully solved the IT dilemma. Irving is highly likely to replace IT's production, has the capacity to improve, and has a contract window that works perfectly with the team's plans.
C's fans need to accept that 2017 IT and going forward asset IT were two very different things. As much as everyone loved him, IT was a looming disaster waiting to happen. His salary expectations, his injury, his size and his contract window vs age did not add up to a stable situation.