What is the Premium Domain Names option? - Help Center—Knowledge Base and FAQ
"If you search for a domain that's already registered, we perform a basic search using the name you entered and provide a list of alternate domain names you may be interested in registering. On the Premium Domains tab, we list domains for which the owners made the domains available for purchase through us.
Purchase a premium domain by adding it to your shopping cart and proceeding through checkout. There are two fees, a transfer fee and a registration fee. We purchase the domain for you, transfer it to your account, and add one year to the existing registration period. We charge subsequent renewals at the normal renewal price. You can access the domain after we complete the transfer process."
--
As far as the $399 .com being better than the 9.99 .net, that's really up to your own judgment. Domainers tend to inflate the sales prices of their domains, and since we don't know what domain it is, it's likely that the domain's 399.00 price tag is based off of the owner's personal opinion of it.
Financially, the .net is easily the better choice between the two, but if you're looking to use the domain to build your business/brand around, you'd eventually want to get the .com version of it as well. Are you willing to pay or negotiate 399.00 for the domain? Do you think you may be able to find an alternative that'll fit just as well, if not better?
If it's just a theoretical question, given just those 2 choices, the .net will usually be the better choice, unless the domain is obviously extremely valuable and you have the money to buy it.
