Last minute pricing for intl business class is often crazy, and this is hardly limited to DL. Last minute US-China/or HKG in F is often over $20,000 USD on UA or CX.
The airlines know that someone booking a US-PVG flight in biz for tomorrow pretty much has to be there and can either expense it or bill it out (ie not price sensitive).
Seems insane to pay $17k for a plane ticket, but can be a small cost relative to a multi-million dollar deal or the cost of not bringing an idled facility back on line etc etc.