I recently did a survey of render farms and wanted to share the info I collected. All costs and times were estimates offered on their websites except for Pixel Plow which I ran a full job.
My computer stats:
i7-3770
3.4 GHz
4 core
8 threads
635 cb (Cinebench R15)
4.75 min/frame
791 frames
62h 37m (estimated render time on my computer)
renderrocket.com $130.52 (Economy Mode) 1h 30m
foxrenderfarm.com $42.48 (Ordinary - 100 nodes) 15m
turborender.com $39.87 (300 nodes) 6m
rebusfarm.net $36.92 (200 nodes) 48m
ranchcomputing.com $32.25 (Emerald) 8m
dropandrender.com $31.73 45m
garagefarm.net $16.00 (Low Priority - 10 nodes) 3hr 35m
rendercore.com $14.00 (Lowest) 15m
I plugged in the same values for all the estimates, the render times are probably the least accurate because there were many options for price tiers that I assume give you faster render times for higher cost, but the prices listed here are all the lowest prices offered.
RenderRocket I actually ran a free test render, they rendered 5 frames and they gave me a really high estimate, I don't know if it was a glitch or if they really are that expensive.
I know this is far from comprehensive and probably not totally accurate to real world use, but I found actual comparative information sorely lacking online other than people just offering the names of websites they use, so I figured this might help someone who is looking for a quick comparison.