How much did you pay him?
Also, general hetroflexible topic, I once got myself a straight well hung twink using the following master tactics:
Me: "So, which way do you swing?"
Him: "I'm straight."
"Have you ever thought about it?"
"No."
"So how do you know?"
"What?"
"Well, if you've never considered it, how could you possibly say for certain what you were?"
"Er... Uhm."
"Just saying."
The next day his first words were "Fuck you" and later on "fuck me".
Best part being I was just messing with him and suddenly he's bi-curious. Unexpected results are best results.