Bony's agent Francis Kacou revealed Swansea's club-record bid of £12million with add-ons, which Vitesse are yet to accept.
Kacou fumed: "Why does it take so long? Six months ago, we agreed a lump sum.
"Swansea wanted to pay and Bony has seen that but Vitesse wanted more.
"We do not know what they want."