All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It is not permissible to raise the price of the furniture which your husband wants to buy for you and make use of tricky methods in order to take his money without his consent, because this is cheating and this is forbidden. The Prophet said: "Whoever cheats us is not one of us." [Muslim] This is taking people’s money without right and Allaah Says (what means): {And do not consume one another’s wealth unjustly.}[Quran 2:188]. Furthermore, this conduct could have a bad effect on your future relationship with this man [your future husband] if he discovers the truth.
Allaah Knows best.