I'm sure the .com owner would have purchased the domain in other extensions if they saw value in it. Generally, I think you would be wasting your time and money trying this as a strategy.
People that own the .com usually don't truly need the .net. It's more of a defensive registration thing.
Selling a .com to the .net holder will be easier, but beware TM issues.
I only deal with .com's and that's all I have in my portfolio of domains. The .com is the only marketable extension there is and people believe in them.