From the July 21, 1906 NYT:

New Fifth Avenue Houses.

Plans have been filed with the Building Department for two residences at 1,014 and 1,015 Fifth Avenue for William Hall's Sons. They are to cost $85,000 each. The architects are Welch, Smith & Provot.

$85,000 in 1906 is about $1.8 million in 2005 CPI adjusted dollars.

I don't know much about New York City, but the current address of 1014/5 Fifth Avenue is right near the Metropolitan Museum of Art. I googled the address and found the Goethe-Institut, a German Cultural outreach effort.

As for the architects, they built elsewhere in the city and the region, including the Duke (as in Duke University) House at 1009 Fifth Avenue, right across from the museum and one of the few remaining mansions on Fifth Avenue.*

* According to Wikipedia