This is somewhat excessive. There are still valid use cases where Virtualbox comes for free - private users or professional users/companies with a relatively small number of workstations (Oracle's going after companies who use a large number of unlicensed installations).

Also, it is still possible to build a free extension pack; it would be a great project. After all, Virtualbox is GPL, and it shouldn't be underestimated the amount of work that has been, and is being, put into it.