The Nets couldn't afford to let Wallace escape, so they paid a premium for him. The market for 14 ppg defensive oriended wing FAs seems to be around $10m a year, with this deal and the one the Wolves jsut offered Batum.
A big market team like the Nets can afford to play their third option $10m a year. Brooklyn can't trot out a 30 win team next season, unless it's one laden with young players with a ton of promise. Since they traded away a ton of high picks to get Williams and Wallace, their only choice is to go all in with those two, and either trade for Howard or sign him next summer.
The Nets will sign Williams, and, if they can't convince the Magic to S and T Lopez and take Brooks, Morrow, and a bunch of draft picks for Howard, let Lopez walk and sign one year bis like Humphries and be ready for Howard next summer.