Architecture
#21046-1: Empire State Building
This set was released on 2 August 2019 in the US. It retails for $129.99 in and with 1,767 pieces it works out to $0.074/piece.
#21042-1: Statue of LIberty
The set was released in the US on 2 June 2018 for $119.99. The set contains 1,685 pieces so it works out to be $0.071/piece.
#21047-1 - LAS VEGAS
Released on September 2018. It costs $39.99 in the US and with 501 pieces, that makes it $0.08 per piece.
#21023-1: Flatiron Building
Released on 2 May 2015 in the US for $39.99. With 471 pieces, that's $0.085 per piece.
#21031-1: Burj Khalifa
Released on 2 January 2016 in the US for $39.99. It contains 333 pieces which works out to be $0.12/piece.