typically, used as an insult toward two men that are 'together' or, more simply, gay..derived from situations in which two could pay together..
could also explain a status of ones relationship in general..
often times used as an insult..
situation number one:two straight guys
kid at counter: "Two strawberry milkshakes?!"
straight guy 1: "yeah that's me, he's got one two.."
Kid at counter: "are you guys paying together?.."
straight guy 2 to straight guy 1: "Bro he totally thinks we're gay"
situation number 2:two straight guys
girl at ice cream counter (window open):"Hey and welcome! what can i get for you today?"
straight guy 1:"hellooo, how are you? im going to get the brownie sundae"
straight guy 2:"can i just get hot fudge on vanilla ice cream? lolz"
girl at ice cream counter (closes window) is laughing and pointing toward straight guys outside then (opens window):"Are you guys paying together?
Situation number 3:two straight guys observe flamboyant looking men in the mall
Straight guy 1: "these dudes totally pay together"
Straight guy 2 looks over and sees a man with a sweater wrapped around his neck with another man with his collar popped: "aha oh yeah most definitely dude"
situation 4:just talking
"yo did you hear about that kid zack?"
"Yeah i heard he pays together with that kid he's always with"
situation 5:gay guy trying to pick up another gay guy
"hey youre seeing sister of traveling pants?"
"do you wana..you know..'pay together'"
"ouuu most definitely big boy ;)"