Why was attendance so high at Grace Episcopal Church?

Let's check out the auction that took place before the consecration of Grace Church in 1846.
As New York City's population migrated north from the southern tip of Manhattan Island, so did its churches. In 1843, Grace Church commissioned young architect James Renwick, whose later crowning achievement was St. Patrick's Cathedral, to design a new church at Broadway and East 10th St. The Gothic building still stands.
Both to help the church financially, as well as to broadcast the parishioners' social status, pews were auctioned off. Pews at Grace Church sold for for a median price of $500 (in today's dollars) apiece, according to the size and location in the sanctuary. Some pews were sold for up to $1,400! In addition to selling the pews, the church received an annual rental fee, per pew, of 6 to 8 percent of the purchase price.
New Yorkers, ever the bargain hunters, "got their money's worth" each Sunday by warming the pews. Other churches in New York City were following the same practice. The price of a pew purchase or rental directly reflected the socioeconomic standing of each church.


(Photo: looking North on Broadway, Museum of the City of New York)

References:
Homberger, Eric. "Mrs. Astor's New York." New Haven: Yale University Press, 2002.
Patterson, Jerry E. "The First Four Hundred." NY: Rizzoli, 2000.