According to an online store in Lithuania called eFoto.it, the upcoming Sigma 105mm f/1.4 DG HSM Art lens for Nikon F-mount is priced at €1,999.00.
According to previous US price and EU price, the US price for Sigma 105mm f/1.4 DG HSM Art lens will be $1,999.00, same as EU price. You can check US price and release date at B&H Photo Video.