It all makes sense if you replace username with domain name.
How much would .com or .net internet domains be worth if auctioned? Many billions..
Buyer of eos domain name will likely be able to make his investment back or sell it later to another account. It is a unique and precious resource on this blockchain.
There will probably be a secondary market in account/domain names soon.
RE: EOS Username For $440,000!?!?!