- Both those were years back so I would not trust the same price as of today.
- Both are good keywords. If you try to sell it off in a place(country) where the online business has matured you will land very low price.
- Target places where the internet is currently getting a spark and you will land a good price as such generic keywords are no longer available in .com .biz is a gTLD and it expands to read business so you can easily market it to sell for some good dollars.
I cannot give you an estimate price though as it really depends on research to mark the price. Do some research on the country you are targeting and based on the CPC rates / competition of the keywords of products selling online at the country you can come around a price range the domain will sell for.
If at all you get more than one person wanting the domain name, setup on auction to reap the best price.
Note: sellonline.com is parked, meaning it could be for sale as well. If your buyer has enough bucks and knowledge to check on that, he will probably go for the .com and you might get a big thanks from .com seller :p