Pre-WWI
UMC Nitro Club 12g 2 3/4" 3 Dr.Eq. 1 1/8 oz. soft shot $36.50/1000; chilled shot $39/1000
Peters Target and High Gun (shot not specified) $37.50/1000
Sears Pointer soft shot $36.20/1000; chilled 38.50/1000
So a box of shells was about $1 which would be about $35 today.
In the 1920s a box was $1.10 - $1.25