x264 Constant Quality: Wide Bitrate Variance?

[ezcry4t3d]

I recently tried encoding using constant quality instead of setting a desired bitrate.
At Q=21.5 and 1024x432
Rambo 2008 averages 2012 Kbps
No Country for Old Men averages just 895 Kbps

Is this kind of bitrate variance typical in encodes set to achieve the same perceived quality? Or am I doing something wrong?

I am using MeGUI to manage my encodes.
Here's the encode settings for both files if needed: cabac=1 / ref=5 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=6 / rdcmp=psy / brdo=1 / mixed_ref=1 / me_range=32 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / chroma_qp_offset=0 / threads=6 / nr=0 / decimate=1 / mbaff=0 / bframes=16 / b_pyramid=1 / b_adapt=1 / b_bias=0 / direct=3 / wpredb=1 / bime=1 / keyint=250 / keyint_min=25 / scenecut=40(pre) / rc=crf / crf=21.5 / rceq='blurCplx^(1-qComp)' / qcomp=1.00 / qpmin=10 / qpmax=51 / qpstep=4 / ip_ratio=1.40 / pb_ratio=1.30 / aq=2:1.00

[smok3]

irc No Country for Old Men is mostly Javier making some nasty faces and not a lot of action, so why not?

[Sharktooth]

bitrate depends on source compressibility that depends on a lot of factors, including motion.
usually action movies require a lot more bitrate than static movies... so yes, it's normal.