Also, I'm absolutely for "overpaying" players. How do you think you sign anyone who's salary isn't capped by the max? You pay them the most money. Incredibly rare is the time a player accepts less money -- and if they do, there's usually some other reason, like chasing a championship, which we can't exactly sell a player on for next year.
Additionally, I think are three other good arguments to not be afraid of "overpaying" this year or next:
1) With the cap spike upcoming, teams will pay more in year 1 to the current class of free agents, factoring in their price on the open market in 2016. The cap will rise 40%. Player salaries will rise a commensurate amount. A player worth $10 mil this year could be worth $14 mil in 2016. Is it overpaying if you give him $12 mil in 2015?
2) Siccessful draft picks like Marcus Smart can subsidize the salaries of other players. Smart is giving production at least equivalent to the MLE, for $2 million less. Sullinger, when healthy, produces more than his $2 million salary next year. Those savings give us the freedom to overpay a bit on veteran free agents. We have a lot of draft picks the next two years -- this gives us more cushion to go extra high on a free agent.
3) The CBA will end after the 2016 season. After the prior two CBAs were signed, an amnesty provision was included. If we really miss on a signing, it is likely the Celtics can fix the problem before the 2017 season using the amnesty (which the C's have not before used).
Note: I'm not advocating to sign any old free agent. But if there's a player that the Celtics want to go after, who is not a "max" player, they should not be afraid to go a little high on the offer.