Strangely enough there is a paper on power consumption of individual components in a mobile phone. Reading your comment made me wonder if there were any data available. See:
http://www.ssrg.nicta.com.au/publications/papers/Carroll_Heiser_10.pdf
This paper shows power usage of RAM in active, idle and suspend states on an Android phone. Active is RAM being actively utilised by an application. Idle is the phone fully awake but applications are not being actively used (but they are loaded). Suspend state is the phone shutting down to a low power mode, suspending all activities (what your phone does most of the time).
Quick summary is that in idle state the phone uses very little power to maintain RAM, but when in the suspend state it uses almost twice as much (from about 3mW to about 6mW). Even though it is doubling power usage, 6mW is still almost nothing compared to the other subsystems (cpu, gpu, audio, lcd, etc.) in these low power states.