I think I spelled out all my assumptions, so you're free to actually read them.
Desmond is worth $108 million with a $7 million/win cost and a starting point of a 3.5 win player in 2016. If you think that is significantly off, feel free to say why. His batting average, OBP, and slugging have all decreased 3 straight seasons, while his K-rate has gone up significantly. He's also a pretty good runner and an okay defender, but his strengths in those areas are unlikely to improve (since they're based on raw athleticism) as he ages. He was worth 4.1 wins last year, is past his peak most likely, and a 3.5 win projection for 2016 assumes a pretty modest decrease next season similar to last season.
It's possible someone will pay him like a 5-win player, or that the cost of doing business will skyrocket next offseason and he'll get $150 million. I have no idea. Like I said, I would welcome it, because it would mean he bounces back next season. If he continues an offensive decline for a 4th straight year, there's no way he gets close to $150 million.