I read somewhere about poker.com selling for 27 million but not sure about the validity of that either.
Business.com wasn't a domain only sale though, business was attached, so I doubt you can classify $345MM as the highest priced domain sold. It's no different than google buying youtube ... I doubt you would say that the youtube.com domain was bought for $1.65 Billion, right?
There is no such thing as a domain only sale. Anything bought for a significant price has some existing business associated with it, whether it is business.com or poker.com or sex.com. There aren't any domaims out there worth millions that have never had a site on them before.
Try pulling up the keywords here at DP on business and/or marketing. There is no such thing as a bad domain in those fields. I bought one the other day for usage that the keyword pulls almost 600 hits a day on overture. Optimized and worked over correctly that could be quite worthwhile; while still being low on the pecking order of keywords.
A domain sale would be one without a business attached.... and no it doesn't need to have an existing business associated with it. People buy it for traffic/brandbility/mindshare which don't need to have a previous business attached.
I think 1-2-3.tv is selling for a few million but again this is a business based on a domain name apparently!