Singular domain versus Plural domains

[domainking131]

Essential.com sold for $250,000 in November 2015 through Media Options.
Essentials.com sold for $32,000 in August 2014 through Hilco Streambank.
The singular was 7.8x the plural.

DataCenter.com sold for $500,000 in June 2014 in a private transaction.
DataCenters.com sold for $190,000 in October 2013 through Domain Name Sales.
The singular was 2.6x the plural.

Ride.com sold for $325,000 in November 2013 through Domain Name Sales.
Rides.com sold for $120,000 in January 2015 through Flippa.
The singular was 2.7x the plural.

Estate.com sold for $165,000 in February 2013 through UpMarketDNS.
Estates.com sold for $23,600 in November 2007 through Sedo.
The singular was 7.0x the plural.

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