Rouundup is so expensive, if you want to kill everything and NOT spend $40 gallon you could use plain old gasoline- but that would be illegal so I am not advising that to anyone. But it works.
But I would never use it to kill all the stuff growing in the cracks in my driveway or in between the brickwork in my walkway (but never around a shrub or tree that you don’t want to die. )
Because that would be wrong, to do on my own property when no one was looking
I was getting Roundup by the 2.5 gallon jug 20 years ago for $112. Mixture was 2% Roundup. Spray rate was 40-50 gallons/acre. For the 16’ swath I was spraying (railroad right-of-way) that was about 2 acres per mile of track. I set up the hi-rail boom truck with a 525 gallon ag tank and could get about 5.5 miles of coverage on one tankload.