4 November 2014 at 22:52:24 MST
Average Visual Art Prices on FA 
515 people replied and after screening for duplicate values, poorly formated responses, anomalous numbers [10,000 USD for a sketch, etc], separating out commissioners from artists; 418 [81.2%] remained. All currencies are reported in USD ; non USD amounts were converted to USD using values available from the World Bank on Sept 8th, 2013. Error bars are reported as +/- 1 Standard Deviation.
The average derived from the entire sample and as you can tell, there is some hella-large standard deviation [as evidenced by those bizarrely large error bars]. I tried to eliminate outliers but that did not significantly improve things, so I had to dig a bit deeper to find out that the study results contain an extremely large bias towards relatively unknown artists [48.8% of the respondents had <10K pageviews].
While this does not invalidate results persay, it does mean that if we want to look at the entire sample, we are gonna hafta take it with a grain of salt because it means that there is a large proportion of "new" artists relative to well established artists on the site - which makes sense. It does mean however, that the average prices are likely lower than we would expect of a more fully representative sample.
Although this study was conducted primarily on Furaffinity, I have no doubt it is applicable to other digital galleries, such as Weasyl, DA and Tumblr as well.