You could argue that Boston's biggest downfall over their last few seasons has been their lack of dept - firstly because they have an uncanny tendancy to get hit by injuries, and secondly because they just haven't had ANY consistent scorer on the bench.
If Boston had even one consistent scoring threat off the bench last season I can all but guarantee you they would have been in the NBA Finals, and quite possibly have banner 18.
By adding Jason Terry, Boston finally got themselves that consistent scorer who could potentially put them over the hump.
Jeff Green has never averaged less than about 15 points per 36 minutes as long as he's been in the NBA, and yes that includes his season with Boston (check the numbers).
Best case scanario nobody gets hurt and Jeff Green gives Boston a second consistent double figure scorer off the bench.
Worst case scenario Boston gets hit AGAIN with injuries, and Jeff Green gives them:
2. Insurance for Terry in case he gets hurt (as a 6th man)
3. Insurance for Pierce in case he gets hurt (as a SF)
4. Insurance for Bass in case he gets hurt (as a PF)
That is a lot of insurance for a team who (in the past) has so desperately lacked exactly that...and if adding Green turns out the difference between a 2nd round exit and a championship ring, he will have earned every cent.
Add to the that fact that he's only about 25 years old and could well develop into a 20/8 (Antawn Jamison) type guy and the contract makes perfect sense.
It's more then I would have liked, but given how critical he is to Boston's roster at this point in time, it's entirely justified.