I personally feel the singular terms flow better with the .biz extension.
That being said.
I see the singular in the low to maybe mid $xxx range.
The plural Geeks.biz in the mid $xx to maybe $1xx range.
These are reseller prices.
Obviously enduser price is what they are willing to pay.
I have sold some very high end terms in the .biz extension over the years.
All the sales were nothing to write home about.
Good Luck.