Depends entirely on what kind of glue. Simple white glue is fairly cheap- a gallon is a few dollars. There some epoxy glues that could be a couple of hundred dollars.
About a gallon
Seeing as you just say 'glue' (which covers hundreds of products) my answer is a bit vague, -but around 10 pounds to a US gallon.
Pvc glue cost about $6.49 a can about 8 ounces.
It cost $1.34 per gallon.
In the 1950s, super glue did not have a cost. It had not yet come to market.
At $3.00/gallon, it will cost $72.
$1.16
$2.19
A gallon of milk cost $1.01 in 1958
How much did a gallon of gas cosy in 1994 ?
$7.25 per gallon.
On average it was $.20 a gallon