Cheap guys who provide offense don't provide a lot of defense. Life is a compromise, Danny. You need a mix.
This is a great signing. Green is athletic, can shoot the 3 and his defense has improved significantly since the last time he was in Boston. He can be an important piece in the 2nd unit. Ainge was reportedly interested in him last year as well. This might be Boston bolstering its line-up, or a sign that there are more moves on the way.
Gerald Green was the James Young before James Young was. Perhaps we'll see Young back in 6 years, more mature and ready to play.