Hi,
why you want to see plan cost in project builder CJ20n? any specific reason please let us know...
every structure report having this kind of feather as CN41n/CNS41 then check these two report.
and lots of hierarchical report is there for seeking plant cost in project as Gokul suggested above.
so in project builder only plan VS actual cost can be look like by network activity.
Regards,
Sanjeev