I was able to find 352 examples where a domain sold publicly, and then later was sold by BuyDomains. I can't guarantee they were the buyer in the original sale, but it is probable. I was also including purchases that were in the sub $100 sales database. Anyway, here are some interesting stats from the flip data:
Average Acquisition Price: $582.32
Median Acquisition Price: $187.50
Average Sale Price: $2,586.15
Median Sale Price: $2,022.00
Average ROI: 2,527%
Highest ROI: 32,780%
Average Hold Time: 3.8 years
Longest Hold Time: 16.1 years
Looking at their Top 100 flips with the best ROI, 80 of them were purchased on GoDaddy and mostly in the $xx range. The average acquisition cost of these Top 100 by ROI was $52.10 and the median was $47.
The acquisition venues break down like this:
GoDaddy: 42.6%
NameJet: 19.3%
SnapNames: 14.8%
Pool: 1.1%
Flippa: 0.9%
Other: 21.3%
Largest gain in terms of dollar value was BikeCity.com, which was purchased at SnapNames in September 2005 for $1,208 and sold in March 2007 for $18,000.
This is obviously only a small fraction of their flips, since many of their acquisitions were probably uncontested backorders, GoDaddy closeouts (which we don't track), probably some hand registrations, bulk purchases from domainers, and so on. But hopefully it's still somewhat interesting/helpful