I wouldn't say that anyone doing any favor to anyone. I look at recent auction as only demand and supply. All rounders and fast bowlers were in demand, batsmen not so much.
Arjun has been part of Mumbai Indian family for very long and from last 2-3 years they are consistently using him as net bowler so it was pretty obvious.
Accusations against Arjun are ridiculous. He has been a part of the Mumbai state squad and have performed well in the domestic tournaments. If you want to remove nepotism, then first get rid of all the businessmen who are ruining cricket, such as the current ICC chairman Greg Barclay. What qualification people like N Srinivasan, Sharad Pawar and Jay Shah have, to run cricket administration?